A screen is placed a distance 40 cm away from an illuminated object. A converging lens is placed between the source and the screen and it is attempted to form the image of the source on the screen. If no position could be found, the focal length of the lens

1. must be less than 10 cm

2. must be greater than 20 cm

3. must not be greater than 20 cm

4. must not be less than 10 cm

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

The muscles of a normal eye are least strained when the eye is focused on an object

1. far away from the eye

2. very close to the eye

3. at about 25 cm from the eye

4. at about 1 m from the eye

A normal eye is not able to see objects closer than \(25~\text{cm}\) because:

When objects at different distances are seen by the eye, which of the following remain constant?

1. The focal length of the eye-lens

2. The object-distance from the eye-lens

3. The radii of curvature of the eye-lens

4. The image-distance from the eye-lens

A person A can clearly see objects between 25 cm and 200 cm. 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. 25 cm to 200 cm

2. 18 cm to 200 cm

3. 25 cm to 300 cm

4. 18 cm to 300 cm

The focal length of a normal eye-lens is about

1. 1 mm

2. 2 cm

3. 25 cm

4. 1 m

The distance of the eye-lens from the retina is x. For a normal eye, the maximum focal length of the eye-lens

1. = x

2. < x

3. > x

4. = 2x

A man wearing glasses of focal length +1m cannot clearly see beyond 1 m

1. if he is farsighted

2. if he is nearsighted

3. if his vision is normal

4. in each of these cases

An object is placed at a distance u from a simple microscope of focal length f. The angular magnification obtained depends

1. on f but not on u

2. on u but not on f

3. on f as well as u

4. neither on f nor on u