1
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
2
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
$${{{R_1}{R_2}} \over {{R_1} - {R_2}}}$$
3
JEE Main 2021 (Online) 16th March Evening Shift
+4
-1
Red light differs from blue light as they have :
A
Different frequencies and same wavelengths
B
Different frequencies and different wavelengths
C
Same frequencies and different wavelengths
D
Same frequencies and same wavelengths
4
JEE Main 2021 (Online) 16th March Morning Shift
+4
-1
The angle of deviation through a prism is minimum when

(A) Incident ray and emergent ray are symmetric to the prism.

(B) The refracted ray inside the prism becomes parallel to its base

(C) Angle of incidence is equal to that of the angle of emergence

(D) When angle of emergence is double the angle of incidence

Choose the correct answer from the options given below :
A
Statements (B) and (C) are true
B
Only statements (A) and (B) are true
C
Statements (A), (B) and (C) are true
D
Only statement (D) is true
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