Waves & Radiation revision set 1

A person uses a surfboard to ride every 30th wave crest towards the beach. The wave crest travels at a speed of 1.6 m / s and the distance between each wave crest is 24 m. How many wave crests does the person surf in one hour?

• 1

• 2

• 8

• 450

Answer explanation

Wavelength = distance between wave crests = 24m

Frequency = number of waves per second = wavespeed÷wavelength = 1.6/24 Hz

In one hour there are 3600 s so

Number of waves per HOUR = 3600 x 1.6/24

= 240

Surf rides 1 wave in 30 so in one hour - 240/30 = 8

Which statement about sound waves is correct?

• They are able to travel through a vacuum.

• They are able to travel through solids.

• They are transverse waves.

• They travel at the same speed in all substances.

Answer explanation

Sounds need particles & are longitudinal and travel at different speeds in liquids, gases and solids

Which type of waves are produced by a television remote controller?

• infra-red waves

• radio waves

• ultraviolet waves

• visible light

Which box shows an example of a transverse wave and an example of a longitudinal wave?

• transverse - light

  longitudinal - radio

• transverse - radio

  longitudinal - sound

• transverse - sound

  longitudinal - water

• transverse - water

  longitudinal - light

Answer explanation

Water and electromagnetic waves are transverse.

Sound is longitudinal.

A radioactive substance emits radiation at a rate of 600 emissions per second.

Four hours later, it emits radiation at a rate of 300 emissions per second.

What is the half-life of the substance and what is the rate of emission after a further four hours?

• half-life - 2 hours

  rate of emission after a further four hours - 0 emissions per second

• half-life - 2 hours

  rate of emission after a further four hours - 150 emissions per second

• half-life - 4 hours

  rate of emission after a further four hours - 0 emissions per second

• half-life - 4 hours

  rate of emission after a further four hours - 150 emissions per second

Answer explanation

Half-life = time for activity to reduce by a half.

after another 4 hours the activity reduces to 1/2 of 300 - 150.

When measuring the emissions from a radioactive rock brought into the laboratory, a teacher mentions that background radiation must be taken into account.

What is this background radiation?

• infra-red radiation from warm objects in the laboratory

• infra-red radiation from the Sun

• ionising radiation from the radioactive rock brought into the laboratory

• ionising radiation in the laboratory when the radioactive rock is not present.

Four students are discussing ideas about radioactive decay.

Which student’s statement is correct?

• 
• 
• 
• 

Answer explanation

β & α emissions change the numbers of nucleons, γ emission does not change change the numbers of nucleons, unstable nuclei emit ionising radiation

The diagram shows five energy levels in an atom (lowest at bottom).

Electromagnetic radiation is incident on the atom. Which transition would be caused by the absorption of the lowest frequency of radiation?

• 1 to 5

• 1 to 2

• 4 to 5

• 5 to 4

Answer explanation

Electron moves up through smallest 'step' between energy levels (when it absorbs the lowest frequency (so lowest energy) radiation

A radioactive isotope of carbon ¹⁴C decays by beta emission to give an isotope of nitrogen ¹⁴N and a beta particle. The equation for the reaction is shown.

What is the value of X and of Y?

• X is 6

  Y is -1

• X is 6

  Y is 1

• X is 8

  Y is -1

• X is 8

  Y is 1

Answer explanation

Beta emission - a neutron turns into a proton and an electron, so atomic number of nucleus increases by 1.

Electron has atomic number of -1

A beta particle is a fast moving electron.

Which statement explains how beta particles are emitted from an atom?

• An electron is emitted as a beta particle from an inner electron shell of the atom.

• An electron is emitted as a beta particle from an outer electron shell of the atom.

• A neutron changes into a proton and a beta particle is emitted from the nucleus.

• A proton changes into a neutron and a beta particle is emitted from the nucleus.