Chapter 3 - Waves

Question 1

What is the formula to calculate the frequency of a wave from the time period

Answer 1

Frequency = 1 / Time

Question 2

What is the formula to calculate the speed of a wave?

Answer 2

Speed = Frequency x Wavelength

Question 3

Define a transverse wave

Answer 3

In transverse waves, the vibrations are at 90 degrees to the direction energy is transferred by the wave

Question 4

Define a longitudinal wave

Answer 4

In longitudinal waves, vibrations are along the same direction as the wave transfers energy

Question 5

Name a use of waves

Answer 5

They can be used as signals to transfer information - e.g. light in optical fibres or radio waves travelling through the air.

Question 6

list all 7 types of Electromagnetic waves in order

Answer 6

Radio Waves -> Microwaves -> Infrared -> visible light -> ultraviolet -> x-rays -> gamma rays

Question 7

What is the wavelength of radio waves?

Answer 7

~10cm

Question 8

What is long-wave radio?

Answer 8

A radio waves with wavelengths of 1-10km, they can be transmitted long distances as the long wavelengths are bent around the earth

Question 9

what is short-wave radio

Answer 9

a radio wave with wavelengths of 10m - 100m they too can be received from long distances as they are reflected off the ionosphere

Question 10

why must you be close to a TV mast to receive the radio waves?

Answer 10

As the waves used to broadcast TV have short wavelengths, they cannot bend around hills. therefore you must be close to the mast to pickup a signal.

Question 11

what effect can microwaves have on the body?

Answer 11

microwaves have a similar frequency to vibrations of many molecules, therefore, they increase the vibrations. This can lead to internal heating - the heating of molecules inside of you (how microwaves heats up food)

Question 12

what effect can Infra-Red light have on the body?

Answer 12

IR makes the surface molecules in a substance vibrate, like microwaves, this has a heating effect. If exposed to high levels of IR the skin can burn

Question 13

what effect does UV radiation have on the body?

Answer 13

UV damages surface cells and can cause blindness. some frequencies of UV are ‘ionising’ so they carry enough energy to knock electrons off atoms causing cell mutation or destruction which can lea to cancer.

Question 14

what effects do Gamma Rays have on the body?

Answer 14

gamma rays are ionising meaning they carry enough energy to knock electrons off atoms causing cell mutation/destruction tissue damage and cancer. They are much higher frequencies than UV radiation meaning they do more damage.

Question 15

a ray of light hits a mirror at an incident angle of 10 degrees to the normal, what is the angle of reflection for the ray of light?

Answer 15

10 degrees

Question 16

what is a critical angle of glass?

Answer 16

~42 degrees

Question 17

what happened if a ray of light is shone through a prism at an angle LESS than the critical angle?

Answer 17

most of the light passes out but a little bit is internally refracted

Question 18

what happens if a ray of light is shone through a prism at an angle EQUAL to the critical angle?

Answer 18

The emerging ray comes out along the surface. there’s a lot of internal refraction

Question 19

what happens if a ray of light is shone through a prism at an angle GREATER than the critical angle?

Answer 19

No light comes out. it’s all internally refracted.

Question 20

what type of wave is sound?

Answer 20

Longitudinal

Question 21

What is the auditory range of a human?

Answer 21

20Hz - 20,000Hz

Question 22

can soundwaves be refracted?

Answer 22

yes

Question 23

what can an oscilloscope display?

Answer 23

soundwaves

Question 24

if you increase the amplitude of a sound wave, what else increases?

Answer 24

Volume

Question 25

if you increase the frequency, what else increases?

Answer 25

Pitch