Polarization, Brewster's law, Polaroids
- The intensity of transmitted light when a polaroid sheet, placed between two crossed polaroids at 22.5^° from the polarization axis of one of the polaroid, is (I_0 is the intensity of polarised light after passing through the first polaroid): Answer: 3. I₀/8 Key idea: apply Malus's law, I=I₀cos²θ , at each polaroid. The middle sheet is at 22.5^° to the first, and 90^°-22.5^°=67.5^... 1
- An unpolarized light beam travelling in air is incident on a medium of refractive index 1.73 at Brewster's angle. Then- Answer: 1. reflected light is completely polarized and the angle of reflection is close to 60^° Key idea: at Brewster's angle tan i_B=μ , an... 1
- An unpolarised light beam strikes a glass surface at Brewster's angle. Then Answer: 1. the reflected light will be completely polarised but the refracted light will be partially polarised. Key idea: At Brewster's ang... 1
- The Brewsters angle i_b for an interface should be : Answer: 3. 45^° < i_b < 90^° Brewster's law: tan i_b=μ , where μ is the relative refractive index of the interface. Since μ>1 for an ordinar... 1
- Unpolarised light is incident from air on a plane surface of a material of refractive index 'μ'. At a particular angle of incidence 'i', it is found that the reflected and refracted rays are perpendicular to each other. Which of the following options… Answer: 3. Reflected light is polarised with its electric vector perpendicular to the plane of incidence When reflected and refracted rays a... 1
- Two Polaroids P_1 and P_2 are placed with their axis perpendicular to each other. Unpolarised light I_0 is incident on P_1. A third polaroid P_3 is kept in between P_1 and P_2 such that its axis makes an angle 45^° with that of P_1. The intensity of… Answer: 2. I₀/8 Key idea: the first polaroid halves unpolarised light; then use Malus's law I=Icos²θ . After P₁ : I₀/2 . After P₃ (45 ^° ):... 1