Ch 7 Light,Colour & Sight Tc

8/3/2019 Ch 7 Light,Colour & Sight Tc

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CHAPTER 7 LIGHT, COLOUR AND SIGHT

1. THE FORMATION OF IMAGES BY PLANE MIRRORS AND LENSES

The characteristics of an image formed on a plane mirror are1. virtual2. inverted laterally3. upright4. the same size as the object5. image distance and object distance from the plane mirror are the same

The characteristics of an image formed by a convex lens are1. virtual or real2. upright or inverted3. diminished or enlarge

The characteristics of an image formed by a concave lens are1. virtual2. upright3. diminished

Object distance is the distance between the object and the optical central.

Image distance is the distance between the image and the optical central.

Optical central is the point at the centre of a lens.

Principal axis is the straight line which passes through the optical central at a rightangle to the axis of the lens.

Focal point is the point on the principal axis where light rays that are parallel to theprincipal axis will converge after passing through a lens.

2. THE FORMATION OF IMAGES BY OPTICAL INSTRUMENTS

1. A periscope consists of two plane mirrors arranged facing one another at an angleof 45.

The image formed by a periscope is virtual, upright and same size as the object

2. A magnifying glass is made of biconvex lens.

The image formed by a magnifying glass is virtual, upright and larger than the actualsize of the object.

3. A microscope consists of two convex lenses, i.e. objective lens and eyepiece.

The focal length of the objective lens of the microscope is shorter than of theeyepiece.

4. A telescope consist of the convex lenses, i.e. objective lens and eyepiece.

The objective lens of the telescope has a longer focal length while the eyepiecehas a shorter focal length.

5. A camera consists of three main parts, which are the lens, the shutter and the film.

The image formed on a photography film is real, invented and smaller than theactual size of the object.

6. In eye - The characteristics of the images formed on the retina and the pin-hole camera arereal, invented and smaller than the actual size of the object.

SES 1511 Kelantan 2007 *The bolded and italic letter is the answer 113


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3. LIGHT DISPERSION

Light dispersion is a process in which white light is split into its colour constituentscalled a spectrum when it passes through a prism.

A spectrum consists of seven colours in this order: red, orange, yellow, green, blue,

indigo and violet.

Light dispersion occurs because each colour constituents travels at a different speedthrough the prism.

Rainbow is formed when sunlight passes through raindrops. The sunlight isrefracted and dispersed into its colour constituents.

4. LIGHT SCATTERING

Light scattering occurs when white light is directed incident to particles like gasmolecules, water vapour and dust, and the light rays are obstructed and reflected.

The light rays will scatter in all directions. Lights with shorter wavelengths are refracted more. Blue light is refracted more than red light.

Examples of light scattering which occurs in natural phenomena are blue sky at noonand red sun during sunset.

5. THE ADDITION AND SUBTRACTION OF COLOURED LIGHT

Primary colours are colours which cannot be obtained from mixing others colours.The primary colours of light are red, blue and green.

Secondary colours are colours produced from adding two primary colours. Thesecondary colours produced from lights are yellow, mangenta ang cyan.

The absorption of coloured light by a coloured filter is called subtraction ofcoloured lights.

A primary-coloured object only reflects light of the same colour.

A secondary-coloured object reflects light of the same colours as well as theprimary colours that form the colour.

Magenta

Blue Red

Green

Yellow

White

Cyan



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6. THE APPEARANCE OF COLOURED OBJECTS

A white object appears white in white light because it reflects all colours while ablack object appears black because all colours are absorbed by it.

The absorption of light by a coloured object is based on the principle of subtraction

of coloured lights.

The rod cell in the retina is sensitive to light of low intensity. This cell is not sensitiveto colours.

The cone cell can detect colour as it is sensitive to high intensity light.

7. THE EFFECTS OF MIXING PIGMENTS

Pigments are materials that absorb certain coloured lights and reflect coloured lightsthat are not absorbed by the pigments.

The primary colours of pigments are red, blue and yellow.

Mixing pigments is based on the principle of subtraction of coloured lights.

Blue Red

Yellow

Orange

Black

Violet

Green

8. THE IMPORTANCE OF COLOUR IN DAILY LIFE

The uses of colour in daily life are printing, electrical writing, traffic lights, symbolsand signals.

The importance of colour to animals is to protect themselves from danger, to attractattention of the females species and to warn other animal to keep away.

The importance of colour to plants include to attract animals for pollination purposesand to warn animals and humans of its toxicity.



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PAPER 1

1. Which of the following causes the formation of image in a plane mirror ?

A. Addition of lightB. Refraction of lightC. Reflection of lightD. Scattering of light

2. What are the characteristics of image formed by the plane mirror?

A. Real, inverted and same sizeB. Virtual, inverted and smaller sizeC. Real, laterally inverted and bigger sizeD. Virtual, laterally inverted and same size

3. The diagram shows an object which is placed in front of a plane mirror.

Object Plane mirror

Which image appears in the plane mirror ?

A..

B.

C

D



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4 . A student stands 3.0 m in front of a plane mirror . If the mirror is moved 1.0m away fromthe student , how far is the image from the student?

A. 3.0mB. 4.0 mC. 6.0 m

D. 8.0 m

5 . The characteristics of an image formed by a concave lens for an object placed at adistance of two focal length are

A. Real, upright and larger sizeB. Real, inverted and same sizeC. Virtual, inverted and larger sizeD. Virtual, upright and smaller size

6 . Which of the following correctly represents the part of a light ray passing through the lens?

D

C

B

A



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7. Which of the following ray diagram is correct?

D

C

B

A

8. A driver wants to overtake the car in front of him, takes a quick look at the side mirror.Which of the following image he has seen?

A. Real and uprightB. Real and invertedC. Virtual and uprightD. Virtual and inverted

9. Which of the following can formed a real image?

A. A plane mirrorB. A convex lensC. A concave lensD. A glass prism

10. Which of the following image cannot be seen on a screen?

A. Real imageB. Virtual imagesC. Inverted imagesD. Diminished image



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11. The diagram shows the position of an object W in front of a convex len. At which of thefollowing positions A,B,C and D is the image of object W formed.

A

Object W

DCB

O3F2FF3F 2F F

12 . Which of the following optical instrument uses plane mirrors?

A. Camera C. TelescopeB. Periscope D. Microscope

13. The diagram shows the word SCIENCE under a magnifying glass.

Magnifying glass

SCIENCE

What is the distance between the word and the lens?

A. Twice the focal length of the lensB. Equal the focal length of the lensC. Less than the focal length of the lensD. More than the focal length of the lens

14. A student uses a convex len to check the internal components of a radio.What is the distance between the lens and the radio in order to see a larger image?

A. Twice the focal lengthB. The same as the focal lengthC. Less than the focal length

D. More than twice the focal length



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15 The diagram shows an image formed by a convex len.

Which of the following optical instrument uses this arrangement?

A. A glassB A projectorC. A magnifying camera

D. A photographic enlarger

16 . Periscope can be formed by using two plane mirrors.Which of the following is the correct arrangement of the mirrors in the periscope?

A CB D

17. The diagram shows an experiment using light.

Light source

Glass PrismViolet

Red

Which of the following process occur in the glass prism?

A. Addition of lightB. Light scatteringC. Dispersion of lightD. Subtraction of light



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18 . Which of the following causes rainbow?

A. Lights is refracted by droplets of water in the atmosphereB. Lights is scattered by dust particles in the atmosphere after rainC. Lights is reflected and scattered by dust particles in the atmosphere after rain

D. Lights is reflected and dispersed by droplets of water in the atmosphere afterrain

19 . The diagram shows a beam of white light passing through a prism and forms aspectrum of light on the white screen.

Which of the following represent he colour of the spectrum at Q?

A. Violet C. YellowB. Red D. Blue

20 . The diagram shows a beam of white light passes through prism R and S.

Which of the following is formed on the screen?

A. Red spotB. Black spotC. White spotD Yellow spot



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21. The diagram shows the structure of a camera

Which of the following is the function of X?

A. Allow the light through

B. Control the amount of lightC. Adjust the position of the imageD. Control the duration of light exposure

22 . Diagram shows a human eyeX

Which part of the camera has a similar function to part X in the human eye?

A. Lens C. DiaphragmB. Aperture D. Focusing ring

23 . The figure shows a pinhole camera with three holes.Which of the following image is formed on the screen?

Screen

Object

Hole



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D

A C

B

24. What happens to the lens of our eyes when we look at a distant object?

A. ThinnerB. ThickerC. ShorterD. No change.

25 . Which of the following pair functions to control the amount of light?

Eye Camera A. Iris Diaphragm

B. Pupil Shutter

C. Cilliary body Focus adjusterD. Retina Lens

26 . Which of the following shows the correct adjustment of the eye when we move from abright room into a dark room?

A. The lens become thinnerB. The lens becomes thickerC. The pupil becomes biggerD. The pupil becomes smaller

27. Why is a colour blind person not able to identify red and green objects ?

A. Damage of irisB. Damage of lensC. Damage of retinaD. Damage of cone cell



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28 . The diagram shows the natural phenomenon of the sky at noon.

Which colour of the sunlight is dispersed most?

A. Blue C. GreenB. White D. Yellow

29. Which of the following statement is correct about light scattering?

A. Light splits into its component coloursB Light is subtracted from its component colours

C. Light is reflected and dispersed into different coloured lightD. Light is reflected and scattered in all directions by suspended particles

30 . At noon the sky is blue. Which of the following cause this phenomenon?

A. Reflection of the blue light from the sea waterB. Reflection of the blue light from the surface of the earthC. Absorption of blue light by the particles in the atmosphereD. Scattering of the blue light by the particles in the atmosphere

31. The diagram shows a blue light passing through a coloured filter.

BlackBlue light

Filter



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Which of the following is the colour of the flter ?

A. Cyan B. Magenta C. Blue D. Yellow

32. The diagram shows a red light and a cyan light which are projected onto a white screen.

What colour can be seen at X,Y and Z?

X Y ZA. Red Magenta BlueB. Blue Cyan YellowC. Blue White YellowD. White Black Red

33 . The diagram shows an overlapping of coloured lights.

What is the colour of light in the shaded area?

A. White C. CyanB. Green D. Blue



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34 . The diagram shows a beam of white light passing through a glass prism. A yellow and

magenta filter is placed between the prism and the screen.

Magentafilter

Yellowfilter

Beam ofwhite light

Glass Prism

White screen

Which of the following colour do you expect to observe on the screen?

A. Red C. Magenta

B. Green D. Yellow

35 . Which of the following pairs of coloured light addition could form white colour?

A. Cyan and redB. green and yellowC. Yellow and cyanD. Magenta and blue

36 . Which of the following statement is correct about black objects?

A. The objects transfer any light

B. The objects reflects any lightC. The objects absorbed any lightD. The objects scattered any light

37. The diagram shows a beam of white light that is allowed to pass through a yellow filter,green filter and red filter.



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What is the colour of P,Q and R?

P Q RA Yellow Green RedB Red Red No light

C Green Red No lightD Yellow Green No light

38 . The figure below shows the overlapping of three primary colours.

Red

Q

Green

Blue

Which of the following colour is formed at Q?

A. White C. IndigoB. Orange D. Magenta

39. Why does a white object appear white?

A. Absorb any lightB. Reflects any lightC. Transmits any lightD. Absorb green light

40. The diagram shows a coloured object under the coloured light.

Eye

Red Object

Blue light

Which of the following is the colour of the object appeared?

A. Blue C. White



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B. Red D. Black41. The diagram shows an experiment on the subtraction of coloured light.

Red light

Green leaf

The colour of the leaf will appearA. Green C. RedB. Black D. Yellow

42. The diagram shows a flower.

Which of the following coloured lights can make the petal appears red?

A. Blue light C. MagentaB. Green light D. Cyan light

43. When certain coloured light is shined on to magenta object, the object appears red.Which of the following is the coloured light?

A. White C. YellowB. Green D. Magenta

44 . The diagram shows the colours of a shirt and skirt seen under different coloured light.

Seen underlight X

Seen underwhite light

Green

Red Black

Green



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What is the colour of light X ?

A. Blue C. RedB. Green D. Yellow

45 . The diagram shows a circular cardboard painted with three different pigments.

BlueRed

White

When the cardboard is seen under a blue light, which of the following is the correctappearance of the cardboard?

Black

Blue

Blue

Red

Blue

A C

Blue

Black

Blue Blue

BD

46. A yellow flower appears red when seen under a red light. Which of the followingstatements is correct about the observation?

A. The yellow flower reflect red light.B. The yellow flower has absorbed the blue colour.C. The mixing of yellow colour and the light gives red colours.D. We only can see the colour of the light and can not see the colour of the flower.

47 . If a white shirt is to be turned to an orange colour, which colour dyes must be used?

A. Blue and green C. Yellow and redB. Red and blue D. Green and red



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48. The diagram shows a batik-printing process

Printing Block

Q

Blue Cloth

Q turns green

What is the original colour of Q?

A. Red C. GreenB. Cyan D. Yellow

49. Which of the following coloured inks are used in colour printing?

A. Red, blue, green and black

B. Blue, green, yellow, and blackC. Cyan, magenta, red and blackD. Magenta, yellow, cyan and black

50. Which of the following is the importance of colours to human being?

A. Helps in pollinationB. Used in electrical wiringC. As a warning to other animalsD. Enable us to hide from danger



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PAPER 2

SECTION A

1. Diagram 1 shows an experiment to measure the focal length of convex lens.

Convex lensWhite screen

Light fromdistance object

Convex lensWhite screen

Light fromdistance object

DIAGRAM 1

Type of convex lens Focal lengthThin lens 8

Thick lens 6

(a) State the hypothesis of the experiment.

.

[ 1 Mark]

The thicker the lens the shorter the focal length

(b) Fill the table above. [2 Marks](c) Name the following variable for the above experiment

(i) Manipulated

.The thickness of convex lens

(ii) Responding

.Focal length

(iii) Constant

. [2 Marks]Light from distance object / Object distance



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(d) What is operational definition for focal length in this experiment?

....

Focal length is the distance of a lens and screen

[ 1 Mark]

2. Diagram 2 shows an experiment using pin-hole camera .

DIAGRAM 2

S

Pin-hole camera

The results of the experiment is shown in the table below

Size of pin-hole Characteristics of image

Small Sharp image

Big Blurred

a) State the hypothesis of the experiment.

.The bigger the size of the pin-hole, the blur the image formed

.

[ 1 Mark]b) What is the observation of the experiment?

.

.

The small size of pin-hole formed sharp image and the bigger size of

pin-hole, formed blur and brighter image.

[ 1 Mark]

c) What inference could be made from the experiment?

.

.

Bigger size of the pin-hole allows more light enter the camera

Bigger size of the pin-hole causes the images to overlap.

[ 1 Mark]



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d) Name the following variable for the above experiment

(i) Manipulated

.The pin-hole size

(iv) Responding

.The image characteristics / Sharp and blur images

(v) Constant

.The size of the object

[3 Marks]

e) Predict the image formed when a convex lens is placed at S in Diagram 3.

.A sharper image will be formed

[1 Mark]

SECTION B

1. Diagram 3 shows the addition of coloured lights.

P

Q

S

R

DIAGRAM 3



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(a) Complete the table below.

Area Colour of light

P Green

Q Cyan

R Magenta

S White

(b) What is the name for colour Q and R?

Secondary colour

[ 1 Mark]

(c) (i) What is the colour of green object located at S?

Green

[ 1 Mark](ii) Give reason for your answer.

The green object reflects green colour under white light.

[ 2

Marks]

2. Diagram 4 shows a periscope. An observer is looking at an object.

Observer

Plane mirror

Object

Obstacle

Plane mirror

DIAGRAM 4



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(a) Draw the light rays reaching the eye of the observer.

[ 1 Mark]

(b) What principle is applied in a periscope.

Reflection of light

[ 1 Mark]

(c) Name one other material which can be used to replace the plane mirror.

Prism

[ 1 Mark]

(d) State one other use of the periscope.

Used in submarines

[ 1 Mark]

3. Diagram 5 shows an object P placed in front of a pinhole camera.

DIAGRAM 5

ObjectZ

Hole Y

Screen

Pinhole camera

(a) Draw a ray diagram to show how an image is formed in diagram 5.[ 1 Mark]

(b) Measure and write the size of image formed.

..............................cm [ 1 Mark]

(c) Predict the characteristics of image if the number of hole Y is increase to three?

.....................................................................................................................

0.9 0.1

Three images are formed

[ 1 Mark](d) Name other optical device which has the same characteristics as the

image produced in Diagram 5.

.....................................................................................................................Camera

[ 1 Mark]

(e) What is the size of image formed if the object is placed at Z?

.....................................................................................................................The image becomes bigger

[ 1 Mark]



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4. Diagram 6 shows a convex lens and an object.

DIAGRAM 6

2F F F

2F

O

(a) Complete the ray diagram above to show the image formed. [ 2 Marks]

(b) Give two characteristics of the image formed.

(i) ..............................................................................

ii) ..............................................................................

Image size is the same as object

Inverted iii) Real

[ 2 Marks]

(c ) If the object is moved far away from the convex lens, what will happen to theimage formed?

.....................................................................................................................The image size becomes smaller than object.

[ 1 Mark]

(d) What is the characteristics of the image if convex lens is replaced with concave

lens?

.....................................................................................................................The image becomes smaller, virtual and upright

[ 1 Mark]

(e) Give one optical instrument that has similar arrangement as shown inDiagram 6.

.Photostat machine

[ 1 Mark]



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5. Diagram 7(a) shows two filters are placed in front of two torchlight X and Y

respectively . The lights falls on the white screen and overlaps as shown inDiagram 7 (b).

DIAGRAM 7(a) DIAGRAM 7(b)

(a) What are the colours seen at A and B?

.....................................................................................................................A Blue B Cyan

[ 1 Mark]

(b) What are the primary colours formed in (a)?

............................................................................................................

Blue

[ 1 Mark]

(c ) If a magenta filter is placed in front of the blue filter Y , what colour is seen at A?

.....................................................................................................................[ 1 Mark]

Blue

(d) A bunches of red roses stands under the B light.What is the colour of the

(i) roses

...........................................................................................................Black

(ii) leaves

............................................................................................................Green

[ 2 Marks]



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SECTION C

1.

The spectacles of old people have shorter focal lengths than those of a student who inlong-sighted. This is because the lenses in their spectacles have a different thickness.

You are given the convex lens with different thickness.

(a) Suggest a hypothesis to investigate the above statement. [1 Mark]

(a) Describe an experiment to test your hypothesis in (a) based on the followingcriteria.

i) Aim of the experiment. [1 Mark]ii) Identification of variables [ 2 Marks]

iii) List of apparatus and materials [1 Mark]iv) Procedure or method [3 Marks]v ) Tabulation of data [1 Mark]vi) Conclusion [1 Mark]

ANSWER

(a) Hypothesis: The thicker the lens, the shorter the focal length.

(b) (i) Aim: To study the focal length of a convex lens with different thickness.

(ii) Variable that is kept constant: Object distance

is manipulated: Thickness of the lens

responds: Focal length

(iii) List of apparatus and material:Metre rule, screen, convex lenses with different thickness,lens holder

(iv) Procedure:

Choose one distance object, put the lens in between the object andscreen /The arrangement of apparatus is set up as shown in the diagrambelow, i.e. facing an object outside the window

The screen is adjusted until a sharp image is formed on it.

The focal length is measured with a meter ruler.

The steps are repeated using lenses of different thickness.



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(v) Tabulation of data :Thickness of the lens Focal length, f/cm

ThinThick

(vi) Conclusion: A thick convex lens has short focal length while a

thin convex lens has long focal length.

2. (a) What are the differences between images formed by a convex lens anda plane mirror ? [4 Marks]

(b) Diagram shows three instruments which use convex lens.

Study the above diagram and develop a concept of optical instruments.

Your answer should be based on the following aspects.

Instruments useconvex lens

Magnifying glass

MicroscopeTelescope

Identify two common characteristics of optical instruments.

Develop an initial concept of a optical instruments.

Give one example of a optical instrument which uses convex lens andone which does not use convex lens.

Give reason for each choice.

Develop the actual concept. [6 Marks]



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ANSWER

a)Image formed by convex lens Image formed by plane mirror

Real images Virtual image Smaller size than object Same size as the object

Inverted Upright

Not laterally inverted Laterally inverted

b) i ) Common characteristics1. Form virtual image2. Image size is bigger than object size.

ii) Initial conceptAn instrument that forms a virtual image and image size is bigger thanobject size is an optical instrument.

iii) Other example- BinocularNon-example periscopes

iv) Binocular because the image size is bigger than object // use convex lens

Periscopes because the image formed is the same size as the object// use plane mirror

v) Actual conceptAn optical instrument is an instrument that forms a virtual image and image size isbigger than object size.

3. (a) Make comparisons between focusing an image in human eye andcamera. [ 4 Marks]

(c) A student wants to look at something behind a wall. However, he unable to doso. Based on your knowledge in science, suggest an apparatus and explain howit works to the student to solve his problem.

Your answer should include the following:

Identify the problem.

Clarification of the problem

Solving methods

Explain the method using. [ 6 Marks]



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ANSWER:

a)

Eye Camera

Mechanism offocusing

Eye-focusing is donewhen thickness of thelens is regulated by theciliarys muscle.

Camera-focusing is doneby regulating the distancebetween the lens and thefilm

Mechanism ofcontrolling theamount of light

Eye-The amount of lightentering the eyes iscontrolled by the iris

Camera-The amount oflight entering the camerais controlled by thediaphragm

b) Identify the problem :

A student wants to look at something behind a wall.

Clarification of the problemHowever, he unable to do so because the wall is high

Solving methodsUse periscope

Explain the method using

Two plane mirrors are arranged parallel to one another at an angle

of 45o. Light rays from the first mirror are projected to the surface of the

second mirror.

The second mirror reflects the light rays to the eyes of thestudent

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Ch 7 Light,Colour & Sight Tc

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