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Published on: 13/10/2020
12th Standard Physics Optics English Medium Free Online Test One Mark questions 2020 - 2021
Download Tamil Nadu 12th Standard Physics question papers, model tests, one-mark questions, important questions, and public exam papers in PDF format. Free study materials and answer keys for TN State Board students.
Questions + Answers key
Take MCQ Physics Test1.
The image formed by a convex mirror of a real object is larger than the object _____________.
when μ <21
when μ > 2f
for all values of μ
for no value of μ
2.
In an experiment of finding the focal length of a concave mirror, a graph is drawn between the magnitudes of u and V. the graph looks like _____________.
3.
The figure shows a cubical room ABCD will the wall CD as a plane mirror. Each side of the room is 3m We placed a camera at the midpoint of the wall AB. At what distance should the camera be focussed to photograph an object placed at ______________.
1.5 m
3 m
6 m
more than 6 m
4.
The figure shows two rays A and B being reflected by a mirror and going as 'A' and 'B' the mirror is ____________.
plane
concave
convex
may be any spherical mirror
5.
Two plane mirrors A and B are aligned parallel to each other, as shown in the figure. A light ray is an incident at an angle of 30° at a point just inside one end of A. The plane of incidence coincides with the plane of the figure. The maximum number of times the ray undergoes reflections (including the first one) before it emerges out is_______________.
28
30
32
34
6.
It is desired to photograph the image of an object placed at a distance of 3m from the plane mirror. The camera which is at a distance of 4.5 m from the mirror should be focused for a distance of ___________.
3 m
4.5 m
6 m
7.5 m
7.
What should be the angle between two plane mirror so that whatever be the angle of incidence, the incident ray and the reflected ray from the two mirrors be parallel to each other _____________.
60°
90°
120°
175°
8.
A plane mirror produces a magnification of ____________.
-1
+ 1
Zero
Between 0 and + ∞
9.
Two plane mirrors are at right angles to each other. A man stands between them and combs hair with his right hand. In how many of the images will he be seen using his right-hand __________.
None
1
2
3
10.
A man runs towards a mirror at a speed 15m/s. The speed of the image relative to the man is _______________.
15 ms-1
30 ms-1
35 ms-1
20 ms-1
11.
Two plane mirrors are at 45° to each other. If an object is placed between them then the number of images will be ________________.
5
9
7
8
12.
Light transmitted by Nicol prism is, _____.
partially polarised
unpolarised
plane polarised
elliptically polarised
13.
A ray of light strikes a glass plate at an angle 60o. If the reflected and refracted rays are perpendicular to each other, the refractive index of the glass is, _____.
\(\sqrt3\)
\(\frac{3}{2}\)
\(\sqrt{\frac{3}{2}}\)
2
14.
When light is incident on a soap film of thickness 5 x 10–5 cm, the wavelength of light reflected maximum in the visible region is 5320 Å. Refractive index of the film will be, _____.
1.22
1.33
1.51
1.83
15.
In a Young’s double-slit experiment, the slit separation is doubled. To maintain the same fringe spacing on the screen, the screen-to-slit distance D must be changed to, _____.
2D
\(\frac{D}{2}\)
\(\sqrt{2}\)D
\(\frac{D}{\sqrt2}\)
16.
A plane glass is placed over a various coloured letters (violet, green, yellow, red) The letter which appears to be raised more is _____.
red
yellow
green
violet
17.
An air bubble in glass slab of refractive index 1.5 (near normal incidence) is 5 cm deep when viewed from one surface and 3 cm deep when viewed from the opposite face. The thickness of the slab is ______.
8 cm
10 cm
12 cm
16 cm
18.
When a biconvex lens of glass having refractive index 1.47 is dipped in a liquid, it acts as plane sheet of glass. This implies that the liquid must have refractive index, ______.
less than one
less than that of glass
greater than that of glass
equal to that of glass
19.
An object is placed in front of a convex mirror of focal length off and the maximum and minimum distance of an object from the mirror such that the image formed is real and magnified.
2f and c
c and \(\infty\)
f and O
None of these
20.
The speed of light in an isotropic medium depends on, ______.
its intensity
its wavelength
the nature of propagation
the motion of the source w.r.t medium
1.
(d)
for no value of μ
2.
(c)
3.
(d)
more than 6 m
4.
(a)
plane
5.
(b)
30
6.
(d)
7.5 m
7.
(b)
90°
8.
(b)
+ 1
9.
(a)
None
10.
(b)
30 ms-1
11.
(c)
7
12.
(c)
plane polarised
13.
n = tan ip = tan 60o = \(\sqrt{3}\)
14.
2n t cos r = (2m + 1) \(\frac{\lambda}{2}\)
For maximum
m = 2 (For visible region), n - refractive index.
cos r = cos 0 = 1
t = 5 x 10-5 x 10-2 = 5 x 10-7 m
\(n=\frac{(2m+1)\frac{\lambda}{2}}{2t}=\frac{5\lambda}{2 \times 2 \times t}\)
\(=\frac{5 \times5320\times10^{-10}}{4 \times 5 \times 10^{-7}}\)
\(=\frac{5 \times5320\times10^{-10}}{20}=1330 \times 10^3\)
n = 1.330
15.
d' = 2d, β' = β, D' = ?
W.K.T, Fringe width
\(\beta = \frac{D\lambda}{d} \Rightarrow D' = \frac{Dd'}{d}\)
\(D' = \frac{D2d}{d}=2D\)
16.
Refractive index for violet is more and wavelength for violet is very low comparing other colours. So, the letter which appears to be raised more is violet.
17.
Apparent depth = 3 + 5 = 8 cm
Real depth = thickness of the slab = t
n = 1.5
\(n=\frac{Real \ depth}{Apparent \ depth}\)
\(\therefore 1.5=\frac{t}{8}\)
t = 1.5 x 8
t = 12 cm
18.
\(\frac{I}{f}=\left(\frac{\mu_{\mathrm{L}}}{\mu_L}-1\right)\left(\frac{1}{R_1}-\frac{1}{R_2}\right)\)
When the biconvex lens of glass dipped in liquid, it acts as a plane sheet of glass.
\(\therefore \mathrm{f}=\infty, \frac{1}{\mathrm{f}}=0 \quad \frac{\mu_g}{\mu_{\mathrm{L}}}-1=0 ; \frac{\mu_{\mathrm{s}}}{\mu_{\mathrm{L}}}=1, \mu_{\mathrm{s}}=\mu_{\mathrm{L}}\)
19.
Convex Mirror is diverging in nature and for all positions of objects, convex mirror forms virtual and erect image.
20.
v = nג
In an isotropic medium, there is no change in the frequency of the light. So, the speed of light depends on wavelength of light.
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