Question

(a) An object is placed 10 cm from a lens of focal length 5 cm. Draw the ray diagrams to show the formation of image if the lens is (i) converging, and (ii) diverging. (b) State one practical use each of convex mirror, concave mirror, convex lens and concave lens.

Answer 1

a)-here f is 5 and u is 10 cm
so u=2f





b)-

Uses of Concave Mirrors

• Concave mirrors are used as shaving mirrors to see a larger image of the face.
• Dentists use concave mirrors to view the back of the tooth. ENT doctors use them for examining the internal parts of the ear, nose and throat.
• They are used as reflectors in the headlights of vehicles, search lights and in torch lights to produce a strong parallel beam of light.
• Huge concave mirrors are used to focus sunlight to produce heat in solar furnaces.

Uses of Convex Mirrors

• Used as rear view mirrors in automobiles as it covers wide area behind the driver.
• Used as reflectors for street light bulbs as it diverges light rays over a wide area.

Uses of Convex Lenses

• Uses in spectacles to correct the defect of vision called hypermetropia or long sightedness
• Used for making a simple camera
• Used as magnifying glasses
• Used in microscopes, telescopes, film projectors, etc.

Uses of Concave Lenses

• Concave lenses are used for correcting myopia or short-sightedness.
• Concave lenses are used on flashlights to magnify the light produced by the bulb.
• Used in peepholes of house doors for security to provide a view of people or objects outside the doors.