H C Verma Solutions for Chapter: Optical Instruments, Exercise 4: EXERCISES

A compound microscope has a magnifying power of $100$ when the image is formed at infinity. The objective has a focal length of $0.5 \mathrm{cm}$ and the tube length is $6.5 \mathrm{cm}.$ Find the focal length of the eyepiece.

A person wears glasses of power $-2.5 \mathrm{D}$. Is the person farsighted or nearsighted? What is the far point of person without the glasses?

A professor reads a greeting card received on his ${50}^{\mathrm{th}}$ birthday with $+2.5 \mathrm{D}$ glasses keeping the card $25 \mathrm{cm}$ away. Ten years later, he reads his farewell letter with the same glasses but he has to keep the letter $50 \mathrm{cm}$ away. What power of lens should he now use?

A normal eye has the retina $2 \mathrm{cm}$ behind the eye-lens. What is the power of the eye-lens when the eye is (a) fully relaxed, (b) most strained?

A nearsighted person cannot see beyond $25 \mathrm{cm}$. Assuming that the separation of the glass from the eye is $1 \mathrm{cm}$, find the power of the lens needed to see distant objects clearly.

A person has a near point at $100 \mathrm{cm}$. What power of lens is needed to read at $20 \mathrm{cm}$ if he/she uses (a) contact lens, (b) spectacles having glasses $2.0 \mathrm{cm}$separated from the eyes?

A lady uses $+1.5 \mathrm{D}$ glasses to have normal vision from $25 \mathrm{cm}$ onwards. She uses a $20 \mathrm{D}$ lens as a simple microscope to see an object. Find the maximum magnifying power, if she uses the microscope (a) together with her glass (b) without her glass. Do the answers suggest that an object can be more clearly seen through a microscope without using the correcting glasses?

A lady cannot see objects closer than $40 \mathrm{cm}$ from the left eye and closer than $100 \mathrm{cm}$ 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 use as the eyepiece?

(b) What magnification can she get with relaxed eye?