1
JEE Main 2019 (Online) 8th April Evening Slot
+4
-1
A convex lens (of focal length 20 cm) and a concave mirror, having their principal axes along the same lines, are kept 80 cm apart from each other. The concave mirror is to the right of the convex lens. When an object is kept at a distance of 30 cm to the left of the convex lens, its image remains at the same position even if the concave mirror is removed. The maximum distance of the object for which this concave mirror, by itself would produce a virtual image would be :-
A
25 cm
B
10 cm
C
20 cm
D
30 cm
2
JEE Main 2019 (Online) 8th April Morning Slot
+4
-1
An upright object is placed at a distance of 40 cm in front of a convergent lens of focal length 20 cm. A convergent mirror of focal length 10 cm is placed at a distance of 60 cm on the other side of the lens. The position and size of the final image will be :
A
20 cm from the convergent mirror, same size as the object
B
40 cm from the convergent mirror, same size as the object
C
40 cm from the convergent lens, same size as the object
D
20 cm from the convergent mirror, twice the size of the object
3
JEE Main 2019 (Online) 8th April Morning Slot
+4
-1
In figure, the optical fiber is $$l$$ = 2m long and has a diameter of d = 20 μm. If a ray of light is incident on one end of the fiber at angle $$\theta _1$$ = 40°, the number of reflection it makes before emerging from the other end is close to: (refractive index of fibre is 1.31 and sin 40° = 0.64)
A
57000
B
55000
C
66000
D
45000
4
JEE Main 2019 (Online) 12th January Evening Slot
+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
$${{2{f_1}{f_2}} \over {{f_1} + {f_2}}}$$
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