Polarisation Brewsters Law Malus Law - UNSOLVED PRACTICE SET
Chapter: Wave Optics | Topic: Polarisation Brewsters Law Malus Law
POLARISATION BREWSTERS LAW MALUS LAW - UNSOLVED PRACTICE SET
Topic: Polarisation Brewsters Law Malus Law
Multiple Choice Questions
Q1. Polarization of light proves that light is a:
- Longitudinal wave
- Transverse wave
- Mechanical wave
- Standing wave
Q2. Unpolarized light of intensity I₀ passes through a polarizer. The intensity of transmitted light is:
- I₀
- I₀/2
- 2I₀
- Zero
Q3. According to Malus' law, when polarized light passes through an analyzer, the transmitted intensity is:
- I = I₀ cos θ
- I = I₀ cos² θ
- I = I₀ sin² θ
- I = I₀ tan θ
Q4. Brewster's angle is the angle of incidence at which
- The reflected ray is completely polarized
- The refracted ray is completely polarized
- Both reflected and refracted rays are completely polarized
- No reflection occurs
Q5. Brewster's law states tha
- tan i_B = μ
- sin i_B = μ
- cos i_B = μ
- cot i_B = μ
Q6. When unpolarized light is incident on a polarizer and the transmitted light passes through an analyzer, the intensity is maximum when the angle between the transmission axes is:
- 0°
- 45°
- 90°
- 180°
Short Answer Questions
Q7. What is polarization of light? Why cannot longitudinal waves be polarized?
Q8. State Malus' law. What happens to the intensity of transmitted light when the analyzer is rotated through 90°?
Q9. State Brewster's law. What is the angle between the reflected and refracted rays at Brewster's angle?
Q10. Why does the sky appear polarized when viewed through a polaroid?
Q11. A beam of unpolarized light is incident on a glass surface at Brewster's angle. Describe the state of polarization of the reflected and refracted rays.
Q12. Why are polaroid sunglasses more effective than ordinary sunglasses in reducing glare?
Long Answer Questions
Q13. Explain the phenomenon of polarization. Describe an experiment to demonstrate that light is a transverse wave using two polaroids.
Q14. State and prove Brewster's law. Show that at Brewster's angle, the reflected and refracted rays are perpendicular to each other.
Q15. State Malus' law and derive it. Explain how it can be used to determine the angle between the transmission axes of a polarizer and an analyzer.
Numerical & Application-Based Problems
Q16. Unpolarized light of intensity 32 W/m² is incident on a polarizer.
(a) Calculate the intensity of light transmitted through the polarizer.
(b) This transmitted light passes through an analyzer whose transmission axis makes an angle of 30° with the polarizer. Calculate the intensity transmitted through the analyzer.
(c) Calculate the angle through which the analyzer should be rotated so that the transmitted intensity becomes one-fourth of the intensity after the polarizer
Q17. Light is incident on a glass surface (refractive index 1.5) at Brewster's angle.
(a) Calculate Brewster's angle.
(b) Calculate the angle of refraction.
(c) Verify that the reflected and refracted rays are perpendicular to each other.
(d) Calculate the degree of polarization of the reflected light.
Q18. In your school's physics lab, a student performs experiments with polaroids and a laser source.
(a) She places two polaroids with their transmission axes parallel and measures the transmitted intensity as I₀. She then rotates the second polaroid by 60°. Calculate the ratio of the new intensity to I₀.
(b) She then places a third polaroid between the first two, with its transmission axis at 30° to the first. Calculate the final transmitted intensity as a fraction of I₀.
(c) The student shines unpolarized light on a water surface (n = 4/3) and observes the reflected light through a polaroid. At what angle of incidence will the reflected light be completely polarized? Calculate this angle.
(d) A classmate wears polaroid sunglasses and looks at the sky at 90° from the sun. He notices that the sky appears darker when he tilts his head. Explain this observation using the concept of polarization by scattering.
(e) In India, many drivers use polaroid sunglasses to reduce glare from wet roads during monsoon. Explain the physics behind this and calculate the Brewster's angle for water (n = 4/3). Why is this particularly effective for horizontal surfaces like roads?