Light Reflection and Refraction Test - 16

Concave mirrors are used by dentist to see the large images of teeth of patients since concave mirrors form enlarged images. Concave mirrors are also used for shaving purpose. Convex mirrors form diminished images. They are used as rear view mirrors in cars, motorcycles, scooters, etc since they giave a wide field of view.

When a lemon is kept in water in a bowl, and is viewed from the outside, it appears larger than its actual size due to refraction. When reflected rays of light travel from the lemon (which is in water) towards the eye (which is in air), the rays travel from a denser medium to a rarer medium and they bend away from the normal to the water surface.

Between P and F

The net power of the lenses placed in contact is given by the algebraic powers of the individual powers.

Net power of the lens combination, P = P₁ + P₂

Out of water, kerosene, turpentine, and diamond, light travels the fastest in water. The speed of light is higher in a optically rarer medium than in a optically denser medium.

The object should be placed at distance of twice the focal length from the pole in front of the convex lens to get a real image, of the size of the object. A convex lens has two principal foci (represented by F₁ and F₂). If an object is placed at 2F₂, the image will be formed at 2F_1.

According to the law of reflection, the angle of incidence is equal to the angle of reflection. This law of reflection holds good for all types of mirrors - whether plane or spherical, and all types of reflecting surfaces - whether regular or irregular. This law does not apply to transparent lenses.

Mathematically, a plane mirror can be considered to be the limit of either a concave or a convex spherical mirror, and therefore the focal length of plane mirror becomes infinite.

When an object is kept at the centre of curvature of a concave mirror, the image is also formed at the centre of curvature. The distance of the centre of curvature from the pole of the mirror is 2f where f is the focal length of the concave mirror. Therefore, the distance between the pole of the mirror and the image is 2f.