Optical Instruments Physics - Optical Instruments

The maximum focal length of the eye-lens of a person is greater than its distance from the retina. The eye is:

1. Always strained in looking at an object.
2. Strained for objects at large distances only.
3. Strained for objects at short distances only.
4. Unstrained for all distances.

The size of an object as perceived by an eye depends primarily on:

1. Actual size of the object.
2. Distance of the object from the eye.
3. Aperture of the pupil.
4. Size of the image formed on the retina.

In which of the following the final image is erect?

1. Simple microscope.
2. Compound microscope.
3. Astronomical telescope.
4. Galilean telescope.

 A normal eye is not able to see objects closer than 25cm because:

1. The focal length of the eye is 25cm.
2. The distance of the retina from the eye-lens is 25cm.
3. The eye is not able to decrease the distance between the eye-lens and the retina beyond a limit.
4. The eye is not able to decrease the focal length beyond a limit.

A person A can clearly see objects between 25cm and 200cm. Which of the following may represent the range of clear vision for a person B having muscles stronger than A, but all other parameters of eye identical to that of A?

1. 25cm to 200cm.
2. 18cm to 200cm.
3. 25cm to 300cm.
4. 18cm to 300cm.

Can the image formed by a simple microscope be projected on a screen without using any additional lens or mirror?

A person is viewing an extended object. If a converging lens is placed in front of his eyes, will he feel that the size has increased?

The angular magnification of a system is less than one. Does it mean that the image formed is inverted?

A Galilean telescope is 27cm long when focused to form an image at infinity. If the objective has a focal length of 30cm, what is the focal length of the eyepiece?

A farsighted person cannot see objects placed closer to 50cm. Find the power of the lens needed to see the objects at 20cm.

A nearsighted person cannot clearly see beyond 200cm. Find the power of the lens needed to see objects at large distances.

Can virtual image be formed on the retina in a seeing process?

A simple microscope has a magnifying power of 3.0 when the image is formed at the near point (25cm) of a normal eye.

1. What is its focal length?
2. What will be its magnifying power if the image is formed at infinity?

A magnifying glass is a converging lens placed close to the eye. A farsighted person uses spectacles having converging lenses. Compare the functions of a converging lens used as a magnifying glass and as spectacles.

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

A person has near point at 100cm. What power of lens is needed to read at 20cm if he/ she uses.

1. Contact lens,
2. Spectacles having glasses 2.0cm separated from the eyes?

By mistake, an eye surgeon puts a concave lens in place of the lens in the eye after a cataract operation. Will the patient be able to see clearly any object placed at any distance?

A child has near point at 10cm. What is the maximum angular magnification the child can have with a convex lens of focal length 10cm?

A lady cannot see objects closer than 40cm from the left eye and closer than 100cm from the right eye. While on a mountaineering trip, she is lost from her team. She tries to make an astronomical telscope from her reading glasses to look for her teammates.

1. Which glass should she use as the eyepiece?
2. What magnification can she get with relaxed eye?

An eye can distinguish between two points of an object if they are separated by more than 0.22mm when the object is placed at 25cm from the eye. The object is now seen by a compound microscope having a 20D objective and 10D eyepiece separated by a distance of 20cm. The final image is formed at 25cm from the eye. What is the minimum separation between two points of the object which can now be distinguished?

A compound microscope consists of an objective of focal length 1cm and an eyepiece of focal length 5cm. An object is placed at a distance of 0.5cm from the objective. What should be the separation between the lenses so that the microscope projects an inverted real image of the object on a screen 30cm behind the eyepiece?

A lady uses +1.5D glasses to have normal vision from 25cm onwards. She uses a 20D lens as a simple microscope to see an object. Find the maximum magnifying power if she uses then microscope

1. Together with her glass
2. Without the glass. Do the answers suggest that an object can be more clearly seen through a microscope without using the correcting glasses?

An optical instrument used for angular magnification has a 25D objective and a 20D eyepiece. The tube length is 25cm when the eye is least strained.

1. Whether it is a microscope or a telescope?
2. What is the angular magnification produced?

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