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Published on: 13/10/2020
12th Standard Physics Optics English Medium Free Online Test One Mark questions with Answer Key 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.
A concave mirror forms an image of sun at a distance of 12 cm from it __________.
The radius of curvature of this mirror is 6 cm
To use it as a shaving mirror, it must be held at a distance of 8 - 10 cm from the face
If an object is kept at a distance of 12 cm from it, the image formed will be same size as the object
All the above
2.
A cube of side 2m is placed in front of a concave mirror focal length 1m with its face P at a distance of 3m and face Q at a distance of 5m from the mirror. The distance between the images of face P and Q and height of images P and Q are ________________.
1m, O.5m,0.25m
0.5m, 1m, 0.25m
0.5 m, 0.25m, 1m
0.025m, 1m, 0.5m
3.
A rear mirror of a vehicle is cylindrical having a radius of curvature of 10 cm. The length of the arc of the curved surface is also 10 cm. If the eye of the driver is assumed to be at a large distance, from the mirror, then the field of view in radian is ____________.
0.5
1
2
4
4.
A convex mirror of focal length 10 cm forms an image that is half of the size of the object. The distance of the object from the mirror is ____________.
10 cm
20 cm
5 cm
15 cm
5.
A dentist uses a small mirror that gives a magnification of 4 when it is held 0.60 cm from a tooth. The radius of curvature of the mirror is ____________.
1.60 cm (convex)
0.8 cm (concave)
1.60 cm (concave)
0.8 cm (convex)
6.
An object 5 cm tall is placed 1m from the concave spherical mirror which has a radius of curvature of 20 cm. The size of the image is _____________.
0.11 cm
0.50 cm
0.55 cm
0.60 cm
7.
The radius of curvature of a convex mirror is 40 cm and the size of the object is twice as that of the image than the image distance is ______________.
10 cm
20 cm
40 cm
30 cm
8.
Which of the following forms a virtual and erect image for all positions of the object?
Convex lens
Concave lens
Convex mirror
both b & c
9.
An object is placed, 40 cm from a concave mirror of focal length 20 cm, the image formed is ______________.
Real, inverted and same in size
Real, inverted and smaller
Virtual, erect and larger
Virtual, erect and smaller
10.
The minimum distance between the object and its real image for concave mirror is _______________.
f
2f
4f
Zero
11.
A concave mirror of focal length 15 cm forms an image having twice the linear dimensions of the object. The position of the object when the image is virtual will be ______________.
22.5 cm
7.5 cm
7.5 cm
45 cm
12.
An object 2.5 cm high is placed at a distance of 10 cm from a concave mirror of radius of curvature 30 cm. The size of the image is _______________.
9.2 cm
10.5 cm
5.6 cm
7.5 cm
13.
Convergence of concave mirror can be decreased by dipping in ______________.
Water
Oil
Both
None of these
14.
If an object moves towards a plane mirror with a speed V at an angle θ to the perpendicular to the plane of the mirror, find the relative velocity between the object and the image ____________.
V
2V
2 V cosθ
2 V sin θ
15.
16.
One of the of Young’s double slits is covered with a glass plate as shown in figure. The position of central maximum will,_____.
get shifted downwards
get shifted upwards
will remain the same
data insufficient to conclude
17.
18.
Two coherent monochromatic light beams of intensities I and 4I are superposed. The maximum and minimum possible intensities in the resulting beam are _____.
5I and I
5I and 3I
9I and I
9I and 3I
19.
The radius of curvature of curved surface at a thin planoconvex lens is 10 cm and the refractive index is 1.5. If the plane surface is silvered, then the focal length will be, ______.
5 cm
10 cm
15 cm
20 cm
20.
A rod of length 10 cm lies along the principal axis of a concave mirror of focal length 10 cm in such a way that its end closer to the pole is 20 cm away from the mirror. The length of the image is, ______.
2.5 cm
5cm
10 cm
15cm
1.
(d)
All the above
2.
(d)
0.025m, 1m, 0.5m
3.
(b)
1
4.
(a)
10 cm
5.
(c)
1.60 cm (concave)
6.
(c)
0.55 cm
7.
(a)
10 cm
8.
(d)
both b & c
9.
(a)
Real, inverted and same in size
10.
(d)
Zero
11.
(d)
45 cm
12.
(d)
7.5 cm
13.
(d)
None of these
14.
(c)
2 V cosθ
15.
(d)
16.
(b)
get shifted upwards
17.
(b)
18.
I = l1 + l2 + 2\(\sqrt{I_1I_2}\)cos θ
If cos θ = cos 0 = l, I is max
= I+ 4I + 2\(\sqrt{41^2}\) cos 0
= 5I + 4I = 91
If cos π = -1, I is min
Imin = I + 4I + 2\(\sqrt{41^2}\) cos π
= 5I + 4I(-1)
= 5I + 4I = I
(Imax, Imin)= (9I, I)
19.
\(\frac{1}{f} =(n-1)\left(\frac{1}{R_1}-\frac{1}{R_2}\right) \)
\(=(1.5-1)\left(\frac{1}{\infty}-\frac{1}{(-10)}\right)\)
(Since plano convex lens)
\(=0.5\left[\frac{1}{10}\right]=\frac{1}{20} \)
\(\mathrm{f}_t =20 \mathrm{~cm}\)
Formula for silvered lenses
\(\frac{1}{\mathrm{~F}} =\frac{2}{\mathrm{f}_1}+\frac{1}{\mathrm{f}_m} \)
\(\frac{1}{\mathrm{~F}} =\frac{2}{20}+\frac{1}{\infty} \)
\(\therefore \mathrm{F} =\frac{20}{2}=10 \mathrm{~cm}\)
20.
At end A,
\(\frac{1}{f} =\frac{1}{u_A}+\frac{1}{v_A} \)
\(\therefore \frac{1}{v_A} =\frac{1}{-10}-\frac{1}{-20} \)
\(\frac{1}{v_A} =-\frac{1}{10}+\frac{1}{20}=\frac{-2+1}{20}=-\frac{1}{20} \)
\(v_A =-20 \mathrm{~cm} \)
\(\left|v_{\wedge}\right|=20 \mathrm{~cm}\)
At end B,
\(\frac{1}{f} =\frac{1}{u_B}+\frac{1}{v_B} \)
\(\frac{1}{v_B} =\frac{1}{f}-\frac{1}{u_B}, \)
\(u_B =-30 \mathrm{~cm} \)
\(\frac{1}{v_B} =-\frac{1}{10}+\frac{1}{30} \)
\(=\frac{-3+1}{30}=\frac{-2}{30}=\frac{-1}{15} \)
\(v_B =-15 \mathrm{~cm} \)
\(\left|v_B\right| =15 \mathrm{~cm} \)
\(\therefore \quad\left|\mathrm{v}_{\mathrm{A}}\right|-\left|\mathrm{v}_{\mathrm{B}}\right| \) is the length of the image
= 20 - 15 = 5 cm
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