Waves and their effects

Question 1

Amplitude definition

Answer 1

the height of the wave – from the resting position to the peak. So the distance from trough to peak is double the amplitude. Amplitude of a sound wave corresponds to the volume you hear.

Question 2

wavelength definition

Answer 2

physical length of the wave - it is measured by finding the distance between any two similar points on adjacent waves – e.g. peak to peak, or trough to trough

Question 3

frequency definition

Answer 3

number of complete wave cycles per second. It is measured in hertz (Hz for short). In sound, this corresponds to the pitch we hear (higher frequencies = higher pitch).

Question 4

what are the types of waves?

Answer 4

transverse and longitudinal

Question 5

what is a transverse wave?

Answer 5

Transverse waves travel in a direction perpendicular to the direction of oscillation.

Question 6

what is a longitudinal wave?

Answer 6

Longitudinal waves are more of a ‘push-pull’ – where the particles oscillate parallel to the direction of travel.

Question 7

Describe a longitudinal wave

Answer 7

Instead of having peaks and troughs, they have compressions and rarefactions. A compression is when the slinky is pushed together, and a rarefaction is when it is pulled apart e.g sound wave

Question 8

Describe reflection

Answer 8

This is where a wave simply bounces off a surface. The angle at which it strikes the surface is known as the angle of incidence, and the angle at which it reflects is the angle of reflection. These two angles will always be equal.

Question 9

how are angles measured?

Answer 9

The angles are measured with respect to the ‘normal’ - this is an imaginary line drawn perpendicular to the surface.

Question 10

what is refraction?

Answer 10

when a wave enters a different medium at an angle, it will change direction

Question 11

what happens when light enters a more dense medium?

Answer 11

If a wave enters a more optically dense medium, it will refract towards the normal.

Question 12

refraction changes what?

Answer 12

speed, direction and wavelength not frequency

Question 13

what dictates whether a ray of light will reflect or refract?

Answer 13

That depends on something called the critical angle. If the angle of incidence is smaller than the critical angle, the light ray will pass into the material and refract. However, if the angle of incidence is too shallow i.e. greater than the critical angle, the light ray will reflect, resulting in ‘total internal reflection’.

Question 14

what is diffraction?

Answer 14

the property of waves that allows them to ‘bend around corners’, particularly when the wavelength is of similar size to the gap it’s passing through.

Question 15

flection changes what?

Answer 15

direction not speed and wavelength

Question 16

what are electromagnetic waves?

Answer 16

transverse waves

Question 17

What are the electromagnetic waves in decreasing wavelength?

Answer 17

Radio waves Microwaves Infra-red Visible Light Ultraviolet X-rays Gamma Rays

Question 18

Describe electromagnetic waves

Answer 18

-They can travel in a vacuum (remember visible light reaches us from the sun, through space, which is a vacuum) – sound waves can’t travel in a vacuum as they rely on particles to relay the energy to each other
-They all travel at 3x108 m/s (when in vacuum)

Question 19

what are radio waves and microwaves used for?

Answer 19

for communication, microwaves can also be used to heat water molecules in food

Question 20

what is infra red used for?

Answer 20

Infra-red is basically heat. It’s the type of wave given off by a stove, for instance. It’s also how night vision cameras ‘see’ people; it detects their body heat.

Question 21

what is visible light used for?

Answer 21

red being the longest wavelength (it’s next to infra-red), and violet being the shortest (just before ultra-violet).

Question 22

what is ultraviolet used for?

Answer 22

This is emitted by the sun. It is associated with skin cancer

Question 23

what ares-rays and gamma rays used for?

Answer 23

shortest wavelength, meaning they have the highest frequency, and are therefore dangerous high energy waves. They have enough energy to knock electrons off atoms, turning atoms to ions, which is why they are ‘ionising radiation’. They can increase risk of mutations within cells, leading to cancer. X-rays are used in medical imaging, since they pass through most tissues except bone. Gamma rays can be used in radiotherapy, if they’re highly focused onto a tumour.

Question 24

what is the doppler effect?

Answer 24

the Doppler Effect shows that the wavelength of waves emitted by a moving object will change. If the source of the waves is moving towards you, the waves get “squashed”, decreasing the wavelength. However, the speed stays the same, so the frequency increases. The opposite happens when the source moved away from you.