Home › CBSE Class 10 › Physics › The Human Eye and the Colourful World › Power of a corrective lens is expressed in diopt…
Power of a corrective lens is expressed in dioptres. One dioptre equals:
A1 per metre (m^-1)
B1 metre
C1 centimetre
D1 newton per metre
Answer & Solution
Correct answer: A. 1 per metre (m^-1)
1. Power of a lens is the reciprocal of its focal length in metres.
2. P = 1 / f, where f is in metres.
3. The SI unit of P is m^-1, which is called the dioptre (D).
4. So one dioptre equals 1 per metre.
5. A lens of f = 50 cm has power = 1 / 0.5 = 2 D.
_Source: NCERT Class 10 Science Ch 11 'Human Eye and the Colourful World'_
Related questions
Light from a star changes colour during twinkling because:The ability of the eye to focus on objects at different distances is called:Tyndall effect — the visible path of a beam of light through a colloid — is a result of:An old man cannot read a book held close but can see distant scenes clearly. The defect anTwinkling of stars is caused by:The reddish appearance of the sun at sunrise and sunset is due to:The sky appears BLUE because of:A rainbow is formed by: