LIGHT WAVES

• Light is an electromagnetic wave.

• Its motion is transverse.

• Light travels in straight lines.

Visible light- the set of light wavelengths that stimulate the retina of the eye.

ROY-G-BIV

VISIBLE LIGHT RANGE:

Wavelength: 400nm – 700nm

(1nm= 1x10-9m)

4x10-7m – 7x10-7m

SPEED OF LIGHT:

c = 3 X 108m/s

This is the same for all electromagnetic waves!!!!

AS WAVE LENGTH INCREASES, FREQUENCY DECREASES.

f (Hz)

λ (m)

V = fλ where v is always the speed of light.

ELECTROMAGNETIC SPECTRUM

Infrared rays- frequency is lower than visible light. Responsible for heating the earths atmosphere.(less then 4.3x1014Hz)

Ultraviolet rays- frequency higher than visible light. Responsible for skin cancer. (greater than 7x1014Hz)

Low frequency High frequency

Infrared ROY-G-BIV ultraviolet

High λ Low λ

Low energy high energy

velocity is always 3x108m/s velocity is always 3x108m/s velocity is always 3x108m/s

TERMSLuminous- a body that emits its own light.

Illuminated- Body that reflects light.

Transparent- a medium that allows light to travel through it.

Translucent- distorts light.

Opaque- reflects or absorbs light.

PHOTOMETRY The study and measurement of visible light in terms of its perceived brightness to human vision.

SOURCES OF LIGHTIncandescent light-

object gives off light when heated.

• Neon Light – Light produced when electrons in a tube of gas are excited.

Fluorescent light- Ultraviolet rays strike a white powder coating on the inside of the bulb causing it to glow.

• Black light- High frequency visible light (purple) which can cause other objects to fluoresce or glow.

LED- light emitting diode

• Laser light- Light amplification by stimulated emission of radiation

Laser light is monochromatic (one color) and coherent (in phase). This produces a

small beam instead of scattered light

https://www.youtube.com/watch?v=UG85VgLOdPA