1
JEE Main 2020 (Online) 2nd September Morning Slot
+4
-1
Interference fringes are observed on a screen by illuminating two thin slits 1 mm apart with a light source ($$\lambda$$ = 632.8 nm). The distance between the screen and the slits is 100 cm. If a bright fringe is observed on a screen at a distance of 1.27 mm from the central bright fringe, then the path difference between the waves, which are reaching this point from the slits is close is
A
1.27 $$\mu$$m
B
2.05 $$\mu$$m
C
2.87 nm
D
2 nm
2
JEE Main 2020 (Online) 2nd September Morning Slot
+4
-1
A spherical mirror is obtained as shown in the figure from a hollow glass sphere. If an object is positioned in front of the mirror, what will be the nature and magnification of the image of the object?
(Figure drawn as schematic and not to scale)
A
Inverted, real and unmagnified
B
Inverted, real and magnified
C
Erect, virtual and magnified
D
Erect, virtual and unmagnified
3
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%
4
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
$${h \over {2\left( {\sqrt 2 + 1} \right)}}$$
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