A convex lens is placed in water. Its focal length MCQ with Answer and Explanation

A convex lens is placed in water. Its focal length
A. Increases
B. Becomes zero
C. Remains same
D. Decreases
Answer: Option A
Solution (By JKExamLibrary)
Refractive index relative to water decreases, so power decreases, focal length increases.

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Practice More Physics Questions

Question #1
A wire of resistance 5 Ω is bent into a circle. The effective resistance between ends of a diameter is
A. 10 Ω
B. 2.5 Ω
C. 5 Ω
D. 1.25 Ω

Correct Answer: Option D


Explanation:
Circle total resistance 5 Ω. Across diameter, two halves in parallel, each half 2.5 Ω. Parallel: R = (2.5×2.5)/(2.5+2.5) = 6.25/5 = 1.25 Ω. Equal parallel resistors gives half of each.

This question belongs to: Science Physics
Question #2
The scientist who gave the law of inertia was
A. Kepler
B. Galileo
C. Newton
D. Copernicus

Correct Answer: Option B


Explanation:
Galileo first proposed concept of inertia. Newton formalized.

This question belongs to: Science Physics
Question #3
A galvanometer can be converted into an ammeter by connecting:
A. A low resistance in parallel
B. A high resistance in series
C. A low resistance in series
D. A high resistance in parallel

Correct Answer: Option A


Explanation:
An ammeter must have very low resistance so it does not alter the circuit current it is measuring. To convert a sensitive galvanometer into an ammeter, a very low resistance called a 'shunt' is connected in parallel to it. This diverts most of the current away from the delicate galvanometer coil while still allowing a proportional measurement.

This question belongs to: Science Physics