Waves

Question 1

What is amplitude, wavelength, frequency and period of a wave?

Answer 1

Amplitude-Maximum displacement from undisturbed position.
Wavelength-Distance between same point on two adjacent waves.
Frequency-Number of waves passing a certain point per second.
Period-Amount of time it takes for a full cycle

Question 2

Difference between transverse and longitudinal waves and give example.

Answer 2

Transverse-Oscillations perpendicular to directions of energy transfer
Longitudinal-Oscillations parallel to directions of energy transfer

Question 3

Law of reflection

Answer 3

Angle of incidence=Angle of reflection

Question 4

Difference between specular and diffuse reflextoin

Answer 4

Specular-Reflected in single direction by a smooth surface.

Diffuse-Reflected by a rough surface reflected in many different directions.

Question 5

Explain refraction

Answer 5

When a wave crosses a boundary between two materials at an angle it changed direction. If a wave crosses a boundary and sows down it will bend towards the normal. Wavelength changes but frequency stays the same.

Question 6

What kind of current is used to generate radio wave in an antenna.

Answer 6

Alternating current.

Question 7

Why are microwaves used for satellite communication and mobile phone signals

Answer 7

They can pass through the atmosphere.

Question 8

Give an everyday use of infrared radiation.

Answer 8

Electric ehaters, TV remotes and cooking food.

Question 9

What type of radiation is used in optical fibres?

Answer 9

Visible Light

Question 10

Type of radiation produced by lamps in tanning salons.

Answer 10

UV radiation

Question 11

What does ionising radiation mean?

Answer 11

Radiation that can charge atoms by knocking electrons off.

Question 12

What does radiation dose in sieverts measure?

Answer 12

A measure of the risk of harm from the body being exposed to radiation.

Question 13

Three rules for refraction in a convex lens.

Answer 13

1-Incident rays parallel to the axis refract through the lens and pass through the principal focus on the other side
2-Incident ray passing through principal focus refracts and travels parallel to the axis.
3-Incident ray passing through the centre carries on in the same direction

Question 14

Three rules for refraction in a concave lens.

Answer 14

1-An incident ray parallel to the axis refracts and travels in line with the principal focus.
2-An incident ray passing through the lens towards the principal focus refracts parallel to the axis.
3-Incident ray passing through the centre carries on in the same direction

Question 15

Explain the difference between a real and virtual image.

Answer 15

Real image-Light comes together and forms an image on a “screen”
Virtual image-Rays are diverging so the light appears to come from a different place.

Question 16

Do opaque objects transmit light.

Answer 16

They do not transmit light. When visible light waves hit them they absorb some wavelengths and reflect others.

Question 17

How do colour filters work?

Answer 17

They only transmit certain colours (wavelengths) and absorb others

Question 18

Describe the rates of radiation absorption and emission for an object at a constant temperature.

Answer 18

Rate of absorption is equal to the rate of emission.

Question 19

What is a perfect black body

Answer 19

An object that absorbs all of the radiation that hits it. No radiation is reflected or transmitted.

Question 20

How do absorption, reflection and emission of radiation affect the Earth’s temperature?

Answer 20

If the Earth is absorbing more radiation than emitting it’s temperature will rise. If it is emitting more radiation than absorbing it’s temperature will fall.

Question 21

what is the frequency range of human hearing?

Answer 21

20Hz-20kHz

Question 22

How is ultrasound used in pre-natal scanning, industry and echo sounding?

Answer 22

Pre-natal scanning-If ultrasound waves reach a bounday between two different media some of the waves is reflected back and detected. The timing and distribution is processed by a computer to produce a video image of the foetus.
Industrial imaging-Ultrasound entering a material will usually be reflected by the far side of the material, if there is a flaw such as a crack waves will be reflected sooner.
Echo sounding-Used by boats and submarines to find out the depth of the water or to locate objects in deep water.

Question 23

Describe how S and P waves can be used to explore the structure of the Earth’s core.

Answer 23

By observing how seismic waves are absorbed and refracted scientists can work out where the properties of the earth change. P waves can travel through solids and liquids and are refracted. S-waves can’t travel through liquids (or gases). therefore they can’t pass through the liquid core.