16+17: 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

18-20: What are the missing values in this table showing data for sound waves travelling through different substances?

21. If light his the inside surface of a glass block at a large angle of incidence, it is reflected. The smallest angle at which this occurs is called the ...

• A). angle of refraction
• B). angle of reflection
• C). incident angle
• D). critical angle

22. What is the name of this effect?

• A). Internal reflection
• B). Total internal relection
• C). Mirror image
• D). Reflected imaging

23. Which one of these devices makes use of this effect?

• A). magnifying glass
• B). ray box
• C). optical fibre
• D). laser

24. Which of these gives the range of human hearing?

• A). 2 – 2000 Hz
• B). 20 – 2000 Hz
• C). 2 – 20 000 Hz
• D). 20 – 20 000 Hz

25 -27: The diagram below shows 4 sound waves displayed on an oscilloscope screen.

Which of these diagrams shows...

28. Which of these lines correctly shows the path of a ray of light through a block of glass?

29. The black line in this diagram shows how light is refracted by a a glass block. If a tank full of water was used instead, which red line would show the direction of the new ray?