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# Physics Practical Class 10 - Determination of Focal Length of Concave Mirror and Convex Lens. Viva Questions with Answers

1) What is the law of reflection for a mirror?

The laws of reflection for a mirror are:

• The normal, incident ray and refracted ray all lie in the same plane.
• The angle of refraction and the angle of incidence are equal.

2) Define the radius of curvature.

The radius of curvature, R for a curved mirror, can be defined as the radius of the sphere of a hollow glass of which the spherical mirror is a part.

3) What are the principal focus and principal axis?

For the spherical mirror, a point on the principal axis at which the rays reflected from the mirror meet or appear to meet is known as the principal focus. For a convex mirror, the principal focus lies behind the mirror, whereas for a concave mirror, the principal focus lies in the front of the mirror or lens. The imaginary line passing through the centre of curvature and pole of the spherical mirror is known as the principal axis.

4) What is reflection?

One of the fundamental and main properties of light is reflection. At an interface in-between two different media, when the travelling light ray changes its direction, this type of phenomenon is known as reflection. Reflection is nothing but the images you see in the mirrors.

5) Define refraction.

Refraction is basically the bending of light when it passes from one medium to another. Several devices, such as magnifying glasses, microscopes, corrective lenses etc., use this property of refraction.

6) What is wave optics in physics?

The branch of optics that talks about the study of interference, diffraction, polarization, and other phenomena, is known as wave optics.

7) What is magnification?

Magnification of the lens is basically the ratio of the linear size of the image to the linear size of the object.

m = (linear size of the image/linear size of the object)

8) What is a convex lens?

A lens that is curved outwards is known as a convex lens. Convex lenses are also known as converging lenses. The thickness at the centre of a convex lens is more than its edge. A convex lens has the capability to converge a parallel beam of light into a point.

9) What is a concave lens?

The type of lens with at least one side curved inwards is known as a concave lens. A Biconcave lens is a concave lens with both sides curved inward. Concave lenses are also known as diverging lenses because they spread out or diverge the rays of light that are refracted through it.

10) What are cylindrical lenses?

Cylindrical lenses are those lenses that have a curvature along only one axis. The main purpose of cylindrical lenses is to focus light into a line or to alter laser diode elliptical light into a round beam.