10 minutes maximum! Can you do it in 5?

1. Which of these can be used to polarise light?

• A. Polaroid filters and reflection from plane surfaces.
• B. Coloured filters and reflection from plane surfaces.
• C. Polaroid filters and transmission through a vacuum.
• D. Coloured filters and transmission through a vacuum.

2. Which of the following waves cannot be polarised?

• A. microwave.
• B. sound wave.
• C. X-ray
• D. gamma ray.

3. When a wave of amplitude A0 and intensity I0 passes through a polarising filter the intensity of the transmitted wave is ½I0. This means the transmitted wave amplitude is:

• A. A0
• B. ½ A0
• C. 1/√2 A0
• D. ¼ A0

4. Which of these units can be used to measure the intensity of electromagnetic radiation?

• A. W
• B. W m-2
• C. J
• D. J m-2

5 -8. A light ray passes through 2 polarising filters. The first filter polarises the wave in a vertical plane. The second filter is rotated and the transmitted light I2 observed.

5. Which of these gives the correct terms for the first and second filters?

 First Filter Second Filter A initial stage filter polariser B analyser polariser C polariser amplitude moderator D polariser analyser

6. The intensity of light incident on the first filter is I0. Which of these describes the intensity of light after the second filter I2 when it is held vertically or horizontally?

 Second filter horizontal Second filter vertical A I2 = 0 I2 < I0 B I2 = I0 I2 = I0 C I2 = 0 I2 = I0 D I2 < I0 I2 < 0

7. The final light intensity I2 is compared to I1 , the intensity after the first filter. What is the intensity of I2 when the angle between the two filters is 450, given that cos(450) = 1/√2?

8. Which of the 4 graphs below correctly shows the variation in intensity of the final observed beam I2 as the second filter is slowly rotated through 900 from its initial position? It is initially vertically aligned.

9. Which of the following rely on polarisation to function?

• A. CD discs.
• B. Mobile phone signals.
• C. LED TV screens.
• D. LCD displays.

10. When fishing, people often wear sunglasses to reduce the polarised glare from the light reflected from the water surface.

In which direction is the reflected light polarised, and in which orientation must the polarising filters in the sunglasses be aligned?

 Polarisation of reflected light Alignment of filters in sunglasses A vertically vertically B vertically horizontally C horizontally vertically D horizontally horizontally