1
JEE Main 2019 (Online) 12th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
A plano-convex lens (focal length f2, refractive index $$\mu$$2, radius of curvature R) fits exactly into a plano-concave lens (focal length f1, refractive index $$\mu$$1, radius of curvature R). Their plane surfaces are parallel to each other. Then, the focal length of the combination will be :
A
f1 + f2
B
f1 $$-$$ f2
C
$${R \over {{\mu _2} - {\mu _1}}}$$
D
$${{2{f_1}{f_2}} \over {{f_1} + {f_2}}}$$
2
JEE Main 2019 (Online) 12th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
Formation of real image using a biconvex lens is shown below :

If the whole set up is immersed in water without disturbing the object and the screen positions, what will one observe on the screen ?
A
Image disappears
B
Magnified image
C
Erect real image
D
No change
3
JEE Main 2019 (Online) 12th January Morning Slot
MCQ (Single Correct Answer)
+4
-1
A light wave is incident normally on a glass slab of refractive index 1.5. If 4 % of light gets reflected and the amplitude of the electric field of the incident light is 30 V/m, then the amplitude of the electric field for the wave propagating in the glass medium will be :
A
6 V/m
B
10 V/m
C
30 V/m
D
24 V/m
4
JEE Main 2019 (Online) 12th January Morning Slot
MCQ (Single Correct Answer)
+4
-1
A point source of light, S is placed at distance L in front of the centre of plane mirror of width d which is hanging vertically on a wall. A man walks in front of the mirror along a line parallel to the mirror, at a distance 2L as shown below. The distance over which the man can see the image of the light source in the mirror is

A
d
B
d/2
C
3d
D
2d
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