1. The effects of diffraction are clearest in a demonstration when two quantities are similar. What are these quantities?

• A. Frequency and gap size
• B. Wavelength and gap size
• C. Wavelength and amplitude
• D. Gap size and amplitude

2. Which of the following diagrams best shows light wavefronts passing from air, left to right through a block of glass? (Not all wavefronts are shown).

3. A light ray passes from water into glass. The velocity of light in water is 2.30 x 10⁸ ms^-1 and in the glass is 2.00 x 10⁸ ms^-1. What is the refractive index of the water / glass boundary?

• A. 1.15
• B. 2.00
• C. 2.30
• D. 4.60

4. A light ray is incident on a glass block as shown.

The refractive index of the glass/air boundary is 1.5 and the value of sin(30⁰) is 0.5 .

• A. 3
• B. 1.33
• C. 0.5
• D. 0.75

5. Total internal reflection can occur when light is trapped inside any transparent substance. This is used in optical fibres.

To ensure total internal reflection occurs and the light ray remains inside the substance ...

• A. the refractive index of the substance must be small and the angle θ must be small
• B. the refractive index of the substance must be small and the angle θ must be large
• C. the refractive index of the substance must be large and the angle θ must be small
• D. the refractive index of the substance must be large and the angle θ must be large

6. The intensity I of sound waves is measured at a distance x away from a loud speaker. The amplitude of the sound waves measured is A.

If the amplitude is increased to 4A and then the distance increased to 2x, the measured intensity will be ...

• A. I / 2
• B. 2 I
• C. 4 I
• D. 8 I

7-10: A red laser is directed at two narrow slits as shown in the diagram below. Diffraction occurs, and the two rays P and Q arrive at a point on the screen.

7. Destructive interference between the 2 rays will occur if ...

• A. the path difference is λ
• B. the path difference is λ/2
• C. the slit separation is λ
• D. the slit separation is λ/2

8. The adding together of two waves like this is correctly termed the ...

• A. summation of waves
• B. superposition of waves
• C. negation of waves
• D. vector addition of waves

9. Two waves will produce constructive interference if the phase difference is ...

• A. 720⁰
• B. 540⁰
• C. 450⁰
• D. 180⁰

10. An interference pattern will only occur between any two waves if ...

• A. the amplitude is the same
• B. the phase difference is constant
• C. the angle of diffraction is the same
• D. the waves are from the same source