Tutorial Sheet-5 (Physics-1, 15B11PH111)
(Odd Semester, 2025)
Assignment 3: Bi-quartz polarimeter
[1] Discus Brewster’s law and Malus law [CO1]
[2] A person is suffering with color blindness. Which polarimeter is suitable for him to find the specific
rotation of sugar, biquartz polarimeter or Half shade polarimeter and why? [CO1]
[3] The critical angle for a certain wavelength of light in case of glass slab is 42°. Calculate the Brewster
angle of the glass slab. What will be the Brewster angle of the glass slab when immersed in water (𝜇 =
𝟎 𝟎
1.33 ). [CO2] [Ans. 𝟓𝟔. 𝟐𝟏 ; 𝟒𝟖. 𝟑𝟐 ]
[4] Two polarizing sheets have their polarizing directions perpendicular so that the intensity of the transmitted
light is zero. Through what angle must either sheet be rotated so that the intensity becomes one half of the
initial value? Justify your answer. [CO2]
[5] Plane polarized light is incident on a piece of quartz cut parallel to the axis. Find the least thickness for
which the ordinary and the extraordinary rays combine to form plane polarized light. Given, 𝜇 = 1.5533,
𝜇 = 1.5442 and λ = 500 nm. [Ans: 27.5 μm] [CO3] [Ans. 27.5 𝝁𝒎]
[6] Consider three polarizer’s P1 P2, and P3 placed along an axis as shown in the figure. The pass axis of P1
and P3 are at right angles to each other while the pass axis of P2 makes an angle 𝜃 with that of P1. A beam of
unpolarized light of intensity I0 is incident on P1 as shown. What will be the intensity of light emerging from
𝑰
P3 ? [CO3] [Ans. 𝟎 𝑺𝒊𝒏𝟐 (𝟐𝜽)]
𝟖
[7] A phase retardation plate made by quartz has thickness 0.1436 mm. For what wavelength in the visible
range (400- 750nm) it will act as (i) quarter-wave plate (QWP) & (ii) half wave plate (HWP)? Given 𝜇 =
1.5443 and 𝜇 =1.5533. [Ans. 738 nm, 574 nm, 470 nm for QWP and 517 nm for HWP.] [CO4]
[8] 15% sugar-water solution produces an optical rotation of 35° when kept in a 40 cm tube. How much
optical rotation will be produced by a 10% sugar-water solution when placed in a 20 cm long tube? Find the
𝑫𝒆𝒈
specific rotation of sugar also. [CO4] [Ans. 𝟏𝟏. 𝟔𝟕𝟎 ; 𝟓𝟖. 𝟑𝟑 𝒑𝒆𝒓 𝒈. 𝒎𝑳 𝟏 ]
𝒅𝒎
Self-study
[1] The refractive indices for right and left handed circularly polarised light of wavelength 760 nm for quartz
are 1.53914 and 1.5392 respectively. Find the relative phase difference between the rays and the rotation of
light in radian produced by a plate of thickness 0.6 mm. [CO4] [Ans. 𝟏𝟕. 𝟎𝟓𝟎 , 𝟖. 𝟓𝟑𝟎 ]
[2] 10 cm length of an optically active solution produces a right-hand rotation in the plane of polarization
by 20º and a 30 cm length of another solution produces a left hand rotation in the plane of polarization
by 24º. What will be the optical rotation produced by 15 cm length of the mixture of above solutions in
volume ration 1:2. [CO4] [Ans. -𝟐𝟎 ]
