The power of magnifying glasses given by

Find the focal length of the mirror that forms an image 6.2 cm behind the mirror of an object placed at 26 cm in front of the mirror?

A. −6.58 cm

B. −8.41 cm

C. −7.8 cm

D. −9.6 cm

The lens with a long focal length is

A. not strongly curved only

B. thin only

C. thick

D. not strongly curved and thin

The variation of focal length to form a sharp image on retina is called

A. accommodation

B. aperture

C. retina control

D. Sutter

In concave mirror, the size of image depends upon

A. size of object

B. position of object

C. area covered by object

D. shape of object

When light travelling in a certain medium falls on the surface of another medium, a part of it turns back in the same medium. This phenomenon is called

A. reflection

B. refraction

C. defraction

D. acoustics