If the focal length of a convex lens is 50 cm, then which one of the following is its power?

A ball is released from rest and rolls down an inclined plane as shown in the following figure, requiring 4 s to cover a distance of 100 cm along the plane

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Which one of the following is the correct value of angle $$\theta$$ that the plane makes with the horizontal ? (g = 1000 cm/s²)

The coefficient of areal expansion of a material is 1.6 $$\times$$ 10^$$-$$5 K^$$-$$1. Which one of the following gives the value of coefficient of volume expansion of this material?

The refractive indices of two media and denoted by n₁ and n₂ and the velocities of light in these two media are respectively, v₁ and v₂. If n₂/n₁ is 1.5, then which one of the following statement is correct?