Questions and Solutions part 3

1.    When light is incident on a soap film of thickness 5 × 10–5 cm, wavelength reflected maximum in the visible region is 5320 Å. Refractive index of the film will be
    (a) 1.22    (b) 1.33    (c) 1.51        (d) 1.83.

 1187_wave optics solutions.jpg

2.    A ray of unpolarised light is incident on a glass plate of refractive index 1.54 at polarising angle, then angle of refraction is
    (a) 33    (b) 44    (c) 57        (d) 90

 

 1187_wave optics solutions.jpg

 

3.    Two waves of same intensity produce interference. If intensity at maximum is 4I, then intensity at the minimum will be     
    (a) 0         (b) 2I    
    (c) 3I        (d) 4I.

Solution - (a) 
    I1 = I2 = I = a2 
    Imax. = (a + a)2 + (2a)2 = 4a2 = 4I 
    Imin. = (a - a)2 = 0

4.    First diffraction minima due to a single slit of width 1.0 x 10–5 cm is at 300. Then wavelength of light used is       
    
a. 400 Å   b.   500Å    c.   600Å    d.    700Å

 2176_solution 2010.jpg

5.    Light of wavelength   is normally incident on a slit. Angular position of second minimum from central maximum us 300. Width of the slit should be   
    (a) 12 x 10–5 cm        (b) 18 x 10–5 cm    
    (c) 24 x 10–5 cm        (d) 36 x 10–5 cm

 1154_sample wave optics.jpg

6.    A slit 5 cm wide when irradiated by waves of wavelength 10 mm results in the angular spread of the central maxima on either side of incident light by about    
    (a) 1/2 radian         (b) 1/4 radian    
    (c) 3 radian        (d) 1/5 radian.
                                  
Solution - (d) 
    Angular spread on either side is given by  
         θ = λ/a = λ/5 radians

7.    In Young's double slit experiment, ten slits separated by a distance of 1 mm are illuminated by a monochromatic light source of wavelength 5 x 10–7 m. If the distance between slit and screen is 2 metre, then separation of bright lines in the interference pattern will be       
    (a) 0.5 mm        (b) 1.0 mm
    (c) 1.5 mm        (d) 1.75 mm

 1603_velocity wave.jpg

Related Resources
Diffraction and Polarization

DIFFRACTION a) Diffraction is the bending or...

Wave Nature of Light

WAVE NATURE OF LIGHT Huygens’ Wave Theory...

Youngs Double Slit Experiment

YOUNG’S DOUBLE SLIT EXPERIMENT A train of...

Polarisation and Brewsters Law

POLARISATION Polarisation of two interfering wave...

Displacement of Fringes in Youngs Double Slit Experiment

Displacement of Fringes When a film of...

Questions and Solutions part 2

Questions and Solutions part 2 11. Angular width...

Interference by Thin Film

INTERFERENCE BY THIN FILM A ray of light incident...

Questions and Solutions part 1

Questions and Solutions Part 1 1. In Young's...