Waves 1

Question 1

What is a progressive wave?

Answer 1

a wave that travels through a substance or space.

Question 2

What is moving in phase?

Answer 2

When waves move in the same direction with the same speed. The particles have the same displacement from their mean position.

Question 3

What is out of phase?

Answer 3

When particles in a wave are at different points in their cycle at the same time.

Question 4

What is antiphase?

Answer 4

When particles are seperated by n lambda + lambda/2

Question 5

What is the formula for phase difference?

Answer 5

2pi(x)/lambda, where x is a distance between two points.

Question 6

What happens when a wave reflects off of a denser medium

Answer 6

it undergoes a phase change pi or 180 degrees

Question 7

what is a longitudinal wave

Answer 7

where particles vibrate parallel to the direction of energy propagation

Question 8

What is a transverse wave?

Answer 8

a wave where vibrations are at right angles to the direction of energy propogation

Question 9

In term of longitudinal waves, what are compressions and rarefactions?

Answer 9

compressions - the regions of high pressure
rarefactions - the are regions of low pressure

Question 10

Why does sound travel quickly through solids?

Answer 10

Energy is transferred through inter molecular bonds, and because the bonds are stiff and atoms are tightly packed, it travels quickly.

Question 11

What is the range of em waves

Answer 11

Smallest
- Gamma
- X - rays
- UV
- visible light
- infra-red
- microwaves
- radio waves

Question 12

What are the effects of EM radiation on cells?

Answer 12

• radio waves do little
• microwaves are absorbed by water and fat, forcing them to vibrate, heating food
• Infrared gets absorbed and vibrates, cooking food
• UV can cause cancer

Question 13

How are EM used for communication?

Answer 13

• radio waves transmit TV by superimposing information on to a carrier wave, changing its amplitude or frequency
• some microwaves are used for satellite communication
• infrared and visible light is used in optical fibres.

Question 14

What is polarisation?

Answer 14

When the oscillation of a wave are confined to one plane.

Question 15

What is refraction?

Answer 15

the change of direction at a boundary, when a wave travels from one medium to another. This then causes a change in speed. When a wavelength moves to a denser medium, it slows down and the wavelength gets shorter. They also bend towards the normal.

Question 16

What is the refractive index?

Answer 16

The ratio of a waves speed between two materials.

Question 17

What is snells law?

Answer 17

sin(theta incident)/cos(theta refraction) = constant(n) = n2/n1 where n = the refractive index of each object.

Question 18

What is total internal reflection?

Answer 18

the complete reflection of light at a boundary within a material that has a higher refractive index than its surroundings.

Question 19

What is the critical angle?

Answer 19

the angle of refraction for which the angle of incidence is 90 degrees.