1
JEE Main 2019 (Online) 10th April Morning Slot
+4
-1
One plano-convex and one plano-concave lens of same radius of curvature 'R' but of different materials are joined side by side as shown in the figure. If the refractive index of the material of 1 is $$\mu$$1 and that of 2 is $$\mu$$2, then the focal length of the combination is :
A
$${2R \over { {{\mu _1} - {\mu _2}}}}$$
B
$${R \over {2 - \left( {{\mu _1} - {\mu _2}} \right)}}$$
C
$${R \over { {{\mu _1} - {\mu _2}}}}$$
D
$${R \over {2 \left( {{\mu _1} - {\mu _2}} \right)}}$$
2
JEE Main 2019 (Online) 10th April Morning Slot
+4
-1
A ray of light AO in vacuum is incident on a glass slab at angle 60° and refracted at angle 30° along OB as shown in the figure. The optical path length of light ray from A to B is:
A
2a + 2b/$$\sqrt 3$$
B
2a + 2b/3
C
2a + 2b
D
2$$\sqrt3$$/a + 2b
3
JEE Main 2019 (Online) 9th April Evening Slot
+4
-1
A thin convex lens L (refractive index = 1.5) is placed on a plane mirror M. When a pin is placed at A, such that OA = 18 cm, its real inverted image is formed at A itself, as shown in figure. When a liquid of refractive index μ1 is put between the lens and the mirror, The pin has to be moved to A', such that OA' = 27 cm, to get its inverted real image at A' itself. The value of μ1 will be :-
A
$$\sqrt 3$$
B
3 / 2
C
$$\sqrt 2$$
D
4 / 3
4
JEE Main 2019 (Online) 9th April Evening Slot
+4
-1
A convex lens of focal length 20 cm produces images of the same magnification 2 when an object is kept at two distances x1 and x2 (x1 > x2) from the lens. The ratio of x1 and x2 is :-
A
3 : 1
B
2 : 1
C
5 : 3
D
4 : 3
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