Waves and sounds

What is a wave?

- A wave is a disturbance that travels through a medium from one location to another

- A wave is the motion of disturbance- The frequency of a wave is its most basic factor

which doesn’t change when entering one medium through another.

Types of WavesWAVES

ELCTROMAGNETIC WAVES

MECHANICAL WAVES

MATTER WAVES

TRANSEVERSE WAVES

LONGITUDNAL WAVES

SURFACE WAVES ELECTROMAGNETIC

SPECTRUM

Mechanical Waves-Mechanical waves are produced by a disturbance .

-It requires a medium to travel. Common examples include air, water and sound.

- There are 3 types: Transverse, Longitudinal and Surface

Transverse WavesIn transverse waves the direction of the disturbance is perpendicular To that of the direction of travel of the wave.

They also occur when the source disturbance of the wave follows a periodic motion.

They create crests and troughs while travelling and show polarization.

Longitudinal Waves

In this type of a mechanical wave the direction of disturbanceIs parallel to the direction of the motion of the waves.

Some DefinitionsPolarization : It is the process in which the wave vibrates in only one plane.Reflection: When a wave gets reflected back upon entering a medium is known as reflection.Refraction: When switching from one medium to another when the speed of the wave changes and not the frequency.Diffraction: The spreading of waves when it enters through a small slit is known as diffraction.Wave fronts: It gives the position of the waves at a certain time

Longitudinal waves

• Vibrations parallel to direction of motion

• They produce rare faction and compression

• They do no show polarization

Transverse waves• Vibrations at right

angle to the direction of motion.

• They create crests and troughs

• They do show polarization.

Measuring A Wave The wavelength of a wave is the measure of one crest and one troughWhich Is represented by the Greek letter lambda.

A displacement – distance graph can also be used

The most important equation

Speed of wave = frequency X wavelength

• Light, microwaves, x-rays, and TV and radio transmissions are all kinds of electromagnetic waves. They are all the same kind of wavy disturbance that repeats itself over a distance called the wavelength.

Electromagnetic Radiation

At vacuum they travel with the speed of light, i.e at 300000000 m/s ; They show polarization and Diffraction , thus they are transverse in nature; they obey the general equation; they carry energy From one place to another and can be absorbed by matter to cause heating and other effects;

Radio WavesRadio waves are the waves with the longest wavelength and the lowest Frequency, they are used to carry sound, pictures and other informationOver a long distance, they are reflected by small electrically charged Particles present in the ionosphere which makes long distance radio Reception possible. We use them in our radios , phones and TV’s which All usually have antennae’s on them.

MicrowavesThis comes next in the spectrum. Their most common use is in the microWave. They help in cooking the food, they are also used in mobile phonesAnd TV’s. They are used for radar detection. They are the only waves Which can penetrate light rain, haze, snow, clouds and smoke and canTherefore be used in space for taking images of the Earth. These can haveWavelengths measuring a few centimeters to a foot in length.

InfraredInfrared is emitted by all living organisms in large or small quantity, theycan have wavelengths as long as a pin or as short as a cell. The longerInfrared rays are thermal, i.e. we feel warm due to their emission.The short infrared rays on the other hands are used in devices such as The remote control. They can also be used to cook food faster. We can Take infrared sensitive photos using special cameras.

Visible Light

UltravioletThese rays are what cause are skin tan and some extreme cases skinCancer, but they also produce vitamins. The sun emits these rays the Most. They may not be visible to our eyes but the bumblebee and Other likewise organisms can. They are also used to detect invisible Signatures and causes fluorescent clothes to flouresce.

X-RaysThe most common use of these rays are in X-Ray machines, they can Penetrate objects like clothes to give images of the bones.

Gamma RaysThese are the rays with the shortest wavelengths and highest frequency.Gamma rays are used to kill cells, like the cancerous cells. They are alsoUsed to clean surgical instruments.

Sound WavesIt is a type of longitudinal wave which cannot like light waves travelIn vacuum and is best transmitted by solids followed by liquids and Gases. It displays properties of interference and diffraction.

They are well reflected from hard and flat surfaces causing echo.If the surface is nearer than 15m than the echo joins up with the originalSound, this is called reverberation.

The Speed of SoundThe speed of sound varies depending on the material it travels through.In:AIR(0 degree C ): 330m/s ( for rise of every 1 degree the speed increases by 0.61 m/s)WATER : 1400m/sCONCRETE : 5000m/sSTEEL : 6000m/s

We can find the speed using the general equation and to find the Wavelength we can use the formula Wavelength = velocity /frequency

More about soundHearing capacity of humans is sound waves of frequency with 20Hz to 20,000 Hz.

The 3 properties of sound waves are:1)Pitch – Directly proportional to the frequency2) Loudness – Directly Proportional to the amplitude3) Quality – No instrument except a tuning fork emits a pure note and They have a fundamental note mixed with other notes which are overtones and are exact multiples of the fundamental notes.

Frequencies of sound waves above 20,0000 Hz are called ultrasonic, andObjects with speed slower than sound are called subsonic and vice versaAre called supersonic.

Test YourselfQ.1. Sound is faster in ? Explain

-Air- Water- solid

Q2. The approximate speed of sound in air is________ m/s

-5000- 3 X 100000000

- -1600- -330

Q3. The number of sound vibrations per second is called _______.

- Frequency- Amplitude- Time Period

Q4. Explain Reverberation

Q5. The Greek letter _______ is usually used as a symbol to denote the wavelength. λ (lambda) κ (kappa) δ (delta)

Q6. Name any three differences that exist between

Longitudinal and transverse waves. Also, is sound in vacuum transverse

Or longitudinal?

Q7. If the temperature of a lab is kept at45 degrees Celsius what is

The speed of sound ?

Q8. Identify the wave used in the following

And why are the antennae’s size different?

Q9. A physics student sitting near the bonfire

Is feeling warm, which rays effects are these?

Q10. Identify the wave whoseLight sensitive photo this is and

Which are the more energetic areas?

Bonus QuestionsQ. Suggest the properties of Sound that prove that it is a wave

Q. What are the factors that affect the speed of sound in any medium

Q. If a nurse cleans the surgical instruments just before a surgery , which ray does she use?