The power of a lens is defined as the reciprocal of the focal length. Lens power is measured in dioptres (D). Converging (convex ) lenses have positive focal lengths, so they also have positive power values. Diverging (concave ) lenses have negative focal lengths, so they also have negative power values.

The capacity of a lens to bend the rays of light depends upon the focal length. The smaller the focal length, the greater is the bending of a ray of light and vice- versa. Thus the power of a lens to bend the rays of light is inversely proportional to the focal length of the lens.

20 CM in metres= 20/100m=1/5 metres. power of a lens= 1/1/1/5=5 dioptres……..

Power of Lens and its Unit unit of power is dioptre (D). Hence, one dioptre is the power of a lens of focal length one meter.

Focal length f= 1/p So according to the question power is +2.0 D f= 1/2.0 = 0.5 m In centimeter …the focal length is 50cm. it means that it is biconvex lens having focal length 50 cm. Answer: F= 50 cm.

Answer. Explanation: power of a lens is inversely proportional to itsfocal length, less focal length moreconverging power of lens and hence more magnification. Hence, convex lens of focal length 4cm can be used as magnifying glass.

Answer: the answer is 2 diaptres.

Answer. So, Power of convex lens is + 2.5 D.

Power of lens is known as the inverse of the focal length of the lens measured in meter(m). Power of lense = 1/ focal length in meter. The lense used is a convex lens because the focal length is a positive value. The lense used is a concave lens because the focal length is a negative value.

Concave lens forms a virtual image and so, magnification is always positive. A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens?

Hence, it is a concave lens.

double convex lens

Since, focal length is positive, the lens is convex in nature.