When we see an object, the image formed on the retina is
A. real

B. virtual

C. erect

D. inverted.

A person has near point at 100 cm. What power of lens is needed to read at 20 cm if he/she uses (A) contact lens, (B) spectacles having glasses 20 cm separated from the eyes?

A near-sighted person cannot see beyond 25 cm. Assuming that the separation of the glass from the eye is 1 cm, find the power of lens needed to see distant objects.

The near point and the far point of a child are at 10 cm and 100 cm. If the retina is 20 cm

behind the eye-lens, what is the range of the power of the eye-lens?

A normal eye has retina 2 cm behind the eye-lens when the eye is (A) fully relaxed, (B) most strained?

A professor read a greeting card received on his 50th birthday with + 25 D glasses keeping the card 25 cm away. Ten years later, he reads his farewell letter with the same glasses but he has to keep the letter 50 cm away. What power of lens should he now use?

A person wears glasses of power − 25 D. Is the person farsighted or nearsighted? What is the far point of the person without the glasses?

An astronomical telescope is to be designed to have a magnifying power of 50 in normal

adjustment. If the length of the tube is 102 cm, find the powers of the objective and the eyepiece.

The separation between the objective and the eyepiece of a compound microscope can be adjusted between 98 cm to 118 cm. If the focal lengths of the objective and the eyepiece are 10 cm and 6 cm respectively, find the range of the magnifying power if the image is always needed at 24 cm from the eye.

Find the maximum magnifying power of a compound microscope having a 25 dioptre lens as the objective, a 5 dioptre lens as the eyepiece and the separation 30 cm between the two lenses. The least distance form clear vision is 25 cm.

A lady cannot see objects closer than 40 cm from the left eye and closer than 100 cm from the right eye. While on a mountaineering trip, she is lost from her team. She tries to make an astronomical telescope from her reading glasses to look for her teammates. (A) Which glass should she uses as the eyepiece? (B) What magnification can she get with relaxed eye?