1
JEE Main 2021 (Online) 18th March Morning Shift
+4
-1
In Young's double slit arrangement, slits are separated by a gap of 0.5 mm, and the screen is placed at a distance of 0.5 m from them. The distance between the first and the third bright fringe formed when the slits are illuminated by a mnochromatic light of 5890 $$\mathop A\limits^o$$ is :-
A
1178 $$\times$$ 10$$-$$9 m
B
1178 $$\times$$ 10$$-$$6 m
C
1178 $$\times$$ 10$$-$$12 m
D
5890 $$\times$$ 10$$-$$7 m
2
JEE Main 2021 (Online) 18th March Morning Shift
+4
-1
Your friend is having eye sight problem. She is not able to see clearly a distant uniform window mesh and it appears to her as non-uniform and distorted. The doctor diagnosed the problem as :
A
Astigmatism
B
Myopia with Astigmatism
C
Presbyopia with Astigmatism
D
Myopia and Hypermetropia
3
JEE Main 2021 (Online) 17th March Morning Shift
+4
-1
The thickness at the centre of a plane convex lens is 3 mm and the diameter is 6 cm. If the speed of light in the material of the lens is 2 $$\times$$ 108 ms$$-$$1. The focal length of the lens is ____________.
A
0.30 cm
B
30 cm
C
15 cm
D
1.5 cm
4
JEE Main 2021 (Online) 16th March Evening Shift
+4
-1
The refractive index of a converging lens is 1.4. What will be the focal length of this lens if it is placed in a medium of same refractive index? Assume the radii of curvature of the faces of lens are R1 and R2 respectively.
A
Zero
B
Infinite
C
1
D
$${{{R_1}{R_2}} \over {{R_1} - {R_2}}}$$
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