1
JEE Main 2020 (Online) 7th January Morning Slot
+4
-1
If we need a magnification of 375 from a compound microscope of tube length 150 mm and an objective of focal length 5 mm, the focal length of the eye-piece, should be close to :
A
22 mm
B
12 mm
C
33 mm
D
2 mm
2
JEE Main 2019 (Online) 12th April Evening Slot
+4
-1
A transparent cube of side, made of a material of refractive index $$\mu$$2, is immersed in a liquid of refractive index $$\mu$$1($$\mu$$1 < $$\mu$$2). A ray is incident on the face AB at an angle $$\theta$$(shown in the figure). Total internal reflection takes place at point E on the face BC.
Then $$\theta$$ must satisfy :
A
$$\theta > {\sin ^{ - 1}}\sqrt {{{\mu _2^2} \over {\mu _1^2}} - 1}$$
B
$$\theta < {\sin ^{ - 1}}\sqrt {{{\mu _2^2} \over {\mu _1^2}} - 1}$$
C
$$\theta < {\sin ^{ - 1}}{{{\mu _1}} \over {{\mu _2}}}$$
D
$$\theta > {\sin ^{ - 1}}{{{\mu _1}} \over {{\mu _2}}}$$
3
JEE Main 2019 (Online) 12th April Morning Slot
+4
-1
A concave mirror has radius of curvature of 40 cm. It is at the bottom of a glass that has water filled up to 5 cm (see figure). If a small particle is floating on the surface of water, its image as seen, from directly above the glass, is at a distance d from the surface of water. The value of d is dose to: (Refractive index of water = 1.33)
A
11.7 cm
B
6.7 cm
C
13.4 cm
D
8.8 cm
4
JEE Main 2019 (Online) 10th April Evening Slot
+4
-1
The graph shows how the magnification m produced by a thin lens varies with image distance v. What is the focal length of the lens used?
A
$${{{b^2}} \over {ac}}$$
B
$${{{b^2}c} \over a}$$
C
$${a \over c}$$
D
$${b \over c}$$
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