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12th Grade > Physics

OPTICS MCQs

Wave Optics, Ray Optics Refraction, Ray Optics Fundamentals, Ray Optics Curved Surface Refraction, Ray Optics Curved Mirrors

Total Questions : 111 | Page 1 of 12 pages
Question 1. A ray of light is incident at the glass–water interface at an angle i, it emerges finally parallel to the surface of water, then the value of μg would be 
A Ray Of Light Is Incident At The Glass–water Interface At...
  1.    (43)sini
  2.    1sini
  3.    43
  4.    1
 Discuss Question
Answer: Option B. -> 1sini
:
B
For glass water interface gμω=sinisinr.....(i)and For water-air interface ωμa=sinrsin90......(ii)
gμωxωμa=siniμg=1sini
Question 2. A point source of light B is placed at a distance L in front of the centre of a mirror of width d hung vertically on a wall. A man walks in front of themirror along a line parallel to the mirror at a distance 2L from it as shown. The greatest distance over which he can see the image of the light source in the mirror is
A Point Source Of Light B Is Placed At A Distance L In Front...
[IIT-JEE (Screening) 2000]
  1.    d/2 
  2.    d
  3.    2d
  4.    3d
 Discuss Question
Answer: Option D. -> 3d
:
D
We will draw the two extreme possible incident rays on the mirror and get the corresponding reflected rays. The following geometry will give us the desired result.
According to the following ray diagram

A Point Source Of Light B Is Placed At A Distance L In Front...
A Point Source Of Light B Is Placed At A Distance L In Front...
Question 3. A point object is placed at the center of a glass sphere of radius 6 cm and refractive index 1.5. The distance of the virtual image from the surface of the sphere is
  1.    2 cm
  2.    4 cm
  3.    6 cm
  4.    12 cm
 Discuss Question
Answer: Option C. -> 6 cm
:
C
Using refraction formula 1μ21R=1μ2v1u
in given case, medium (1) is glass and (2) is air
So gμa1R=gμav1u11.516=11.5v16
11.56=1v+1.560.5v=1v+14
1v=11214=212=16v=6cm.
Question 4. S1,S2 are two coherent sources of light. P is a point on the screen such that S2PS1P = 0.01029 cm. Wave length of light used is 6000˙A. The order of the fringe formed at P is
  1.    172, bright
  2.    171, bright
  3.    173, dark
  4.    172, dark
 Discuss Question
Answer: Option D. -> 172, dark
:
D
x=(2n1)λ2
1029×107=(2n1)6000×10102
2×171.5=2n1
344=2n
n=172
Question 5. In Young's double slit experiment, if the two slits are illuminated with separate sources, no interference pattern is observed because
 
  1.    There will be no constant phase difference between the two waves
  2.    The wavelengths are not equal
  3.    The amplitudes are not equal
  4.    None of the above
 Discuss Question
Answer: Option A. -> There will be no constant phase difference between the two waves
:
A
In conventional light source, light comes from a large number of independent atoms, each atom emitting light for about 10-9 sec i.e. light emitted by an atom is essentially a pulse lasting for only 10-9 sec. Light coming out from two slits will have a fixed phase relationship only for 10-9 sec. Hence any interference pattern formed on the screen would last only for 10-9 sec, and then the pattern will change. The human eye can notice intensity changes which last at least for a tenth of a second and hence we will not be able to see any interference pattern. Instead due to rapid changes in the pattern, we will only observe a uniform intensity over the screen.
Question 6. Two coherent light sources S1 and S2 (l= 6000 ) are 1mm apart from each other. The screen is placed at a distance of 25 cm from the sources. The width of the fringes on the screen should be
  1.    0.015 cm
  2.    0.025 cm
  3.    0.010 cm
  4.    0.030 cm
 Discuss Question
Answer: Option A. -> 0.015 cm
:
A
Two Coherent Light Sources S1 And S2 (l= 6000 ) Are 1mm Apar...
Question 7. In the figure S1 and S2 are two narrow slits illuminated by light of wavelength λ and they ae in phase. `P' is a point on the screen which corresponds to 4th minimum then the path difference S2PS1P is equal to 
In The Figure S1 And S2 Are Two Narrow Slits Illuminated By ...
  1.    4λ
  2.    5λ2  
  3.    7λ2  
  4.    2λ
 Discuss Question
Answer: Option C. -> 7λ2  
:
C
x=(2n1)λ2;n=4
=(2×41)λ2
=(81)λ2
=7λ2
Question 8. Velocity of light in glass whose refractive index with respect to air is 1.5 is 2×108m s1 and in certain liquid the velocity of light found to be 2.50×108m s1.The refractive index of the liquid
with respect to air is 
  1.    0.64
  2.    0.80
  3.    1.20
  4.    1.44
 Discuss Question
Answer: Option C. -> 1.20
:
C
Refractice index of glass slab =1.5
Velocity of light in glass =2×108ms1
Velocity of light in liquid =2.50×108ms1
μα1vμliμg=vgvlμl1.5=2×1082.5×108
μl=1.2
Question 9. A monochromatic beam of light passes from a denser medium into a rarer medium. As a result      [CPMT 1972]
  1.    Its velocity increases
  2.    Its velocity decreases
  3.    Its frequency decreases
  4.    Its wavelength decreases
 Discuss Question
Answer: Option A. -> Its velocity increases
:
A
A Monochromatic Beam Of Light Passes From A Denser Medium In...
Question 10. The refractive index of a certain glass is 1.5 for light whose wavelength in vacuum is 6000 . The wavelength of this light when it passes through glass is
[NCERT 1979; CBSE PMT 1993; MP PET 1985, 89]
  1.    4000 Å 
  2.    6000 Å 
  3.    9000 Å 
  4.    15000 Å  
 Discuss Question
Answer: Option A. -> 4000 Å 
:
A
The Refractive Index Of A Certain Glass Is 1.5 For Light Who...

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