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. Frequency and amplitude
• E. Gap size and amplitude

2. Which of the following diagrams shows light wavefronts passing from left to right through a block of glass?

3. A light ray passes from water into glass. The velocity of light in water is 2.30 x 10⁸ m/s and in the glass is 2.00 x 10⁸ m/s. The refrective index of the water / glass boundary is

• A. 0.5
• B. 1.15
• C. 2.00
• D. 2.30
• E. 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 . The value of sin (i) will be

• A. 3
• B. 1.33
• C. 0.5
• D. 0.75
• E. 1.5

5. Total internal relection can occur when light is trapped inside glass . This is used in optical fibres.

To ensure total internal reflection occurs and the light ray remains inside the glass,

• A. the refractive index of the glass must be small and the angle θ must be small
• B. the refractive index of the glass must be small and the angle θ must be large
• C. the refractive index of the glass must be large and 2θ must be greater than 90⁰
• D. the refractive index of the glass must be large and the angle θ must be large
• E. the refractive index of the glass must be small and 2θ must be greater than 90⁰

6. A police car is moving towards a stationary observer with the siren switched on. Compared to the source, the sound as measured by the observer will have

• A. a higher frequency and higher velocity
• B. a lower frequency and a higher velocity
• C. the same frequency and a higher velocity
• D. a higher frequency and the same velocity
• E. a lower frequency and the same velocity

A laser is directed at two narrow silts 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 path difference is λ/4
• D. the slit seperation is λ
• E. the slit seperation is λ/2

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

• A. sumation of waves
• B. superposition of waves
• C. negation of waves
• D. vector addition of waves
• E. phase difference of waves

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

• A. 720⁰
• B. 540⁰
• C. 450⁰
• D. 180⁰
• E. 90⁰

10. A double slit experiment is carried out with red light waves as shown above and the interference pattern is recorded.

Which of the following changes would result in an increase in the seperation of maximum points?

• A. Using blue light of higher intensity
• B. Using red light with a smaller gap between slits
• C. Using red light of higher amplitude
• D. Using red light of higher intensity
• E. Using blue light with a larger gap between slits