• A). v = ƒ λ
• B). v = T λ
• C). v = 1/T
• D). v = T ƒ

14-16: What are the missing values in this table showing data for sound waves travelling through different substances?

17. Which of these statements best completes this sentence?

"Radio waves can be produced by..

• A). all hot objects"
• B). oscillations in electrical circuits".
• C). radioactive decay".
• D). flourescent inks".

18-19: A sound wave is produced by a student banging two wooden blocks together. The student is 50m from a large wall. After 0.3s an echo is heard.

• A).  Sound being refracted by the wall.
• B).  Sound being reflected off the blocks.
• C).  Sound being bounced off the air molecules.
• D).  Sound being reflected by the wall.

• A). 167 m/s
• B). 333 m/s
• C). 15 m/s
• D). 30 m/s

20. The 'period' of a wave is...

• A). the time taken to produce one wave.
• B). the speed of the wave in that substance.
• C). the number of waves produced per second.
• D). the height of the wave from the centre of displacement.

21+22. The diagram shows a ray of light entering a plastic block.

The ray of light bends.

21. This effect is called ...

• A). diffraction
• B). refraction
• C). diffusion
• D). transmission

22. This happens because ...

• A). light has a slower velocity in plastic than in air
• B). light has a higher frequency in plastic than in air
• C). light has a faster velocity in plastic than in air
• D). light has a lower frequency in plastic than in air

23. Which of the following diagrams best shows light wavefronts passing from left to right from air into a block of glass? (Note- not all wave fronts are shown).