1
JEE Main 2020 (Online) 9th January Evening Slot
+4
-1
There is a small source of light at some depth below the surface of water (refractive index = $${4 \over 3}$$) in a tank of large cross sectional surface area. Neglecting any reflection from the bottom and absorption by water, percentage of light that emerges out of surface is (nearly) :
[Use the fact that surface area of a spherical cap of height h and radius of curvature r is 2$$\pi$$rh]:
A
17%
B
34%
C
50%
D
21%
2
JEE Main 2020 (Online) 9th January Morning Slot
+4
-1
A vessel of depth 2h is half filled with a liquid of refractive index $$2\sqrt 2$$ and the upper half with another liquid of refractive index $$\sqrt 2$$ . The liquids are immiscible. The apparent depth of the inner surface of the bottom of vessel will be :
A
$${h \over {\sqrt 2 }}$$
B
$${h \over {3\sqrt 2 }}$$
C
$${3 \over 4}h\sqrt 2$$
D
$${h \over {2\left( {\sqrt 2 + 1} \right)}}$$
3
JEE Main 2020 (Online) 9th January Morning Slot
+4
-1
The aperture diameter of a telescope is 5m. The separation between the moon and the earth is 4 × 105 km. With light of wavelength of 5500 $$\mathop A\limits^o$$, the minimum separation between objects on the surface of moon, so that they are just resolved, is close to :
A
20 m
B
200 m
C
600 m
D
60 m
4
JEE Main 2020 (Online) 8th January Evening Slot
+4
-1
In a double slit experiment, at a certain point on the screen the path difference between the two interfering waves is $${1 \over 8}$$th of a wavelength. The ratio of the intensity of light at that point to that at the centre of a bright fringe is :
A
0.853
B
0.568
C
0.672
D
0.760
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