1
JEE Main 2019 (Online) 8th April Morning Slot
MCQ (Single Correct Answer)
+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
2
JEE Main 2019 (Online) 8th April Morning Slot
MCQ (Single Correct Answer)
+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
3
JEE Main 2019 (Online) 8th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
In an interference experiment the ratio of amplitudes of coherent waves is $${{{a_1}} \over {{a_2}}} = {1 \over 3}$$ . The ratio of maximum and minimum intensities of fringes will be :
A
2
B
4
C
18
D
9
4
JEE Main 2019 (Online) 12th January Evening Slot
MCQ (Single Correct Answer)
+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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