Compound Microscope

Q. 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 cm and the tube length is 6.5 cm. Find the focal length of the eyepiece.

Q. In a compound microscope, the focal length of the objective and the eye lens are 2.5 cm and 5 cm respectively. An object is placed at 3.75 cm before the objective and image is formed at the least distance of distinct vision, then the distance between two lenses will be (i.e. length of the microscopic tube)

1. 11.67 cm
2. 12.67 cm
3. 13.00 cm
4. 12.00 cm

Q.

Microscope is an optical instrument which

1. Enlarges the object

2. Increases the visual angle formed by the object at the eye

3. Decreases the visual angle formed by the object at the eye

4. Brings the object nearer

Q. A compound microscope consists of an objective of focal length 1 cm and an eyepiece of focal length 5 cm. An object is placed at a distance of 0.5 cm 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 30 cm behind the eyepiece?

Q. The magnifying power of a converging lens used as a simple microscope is $\left(1+\frac{D}{f}\right).$ A compound microscope is a combination of two such converging lenses. Why don't we have magnifying power $\left(1+\frac{D}{f_o}\right)\left(1+\frac{D}{f_e}\right)?$ In other words, why can the objective not be treated as a simple microscope but the eyepiece can?

Q. The separation between the objective and the eyepiece of a compound microscope can be adjusted between 9.8 cm to 11.8 cm. If the focal lengths of the objective and the eyepiece are 1.0 cm and 6 cm respectively, find the range of the magnifying power if the image is always needed at 24 cm from the eye.

Q.

When the length of a microscope tube increases, its magnifying power [MNR 1986]

1. Decreases

2. Increases

3. Does not change

4. May decrease or increase

Q. The separation $L$ between the objective $(f=0.5cm)$ and the eyepiece $(f=5cm)$ of a compound microscope is $7cm$.

Where should a small object be placed so that the eye is least strained to see the image?

1. $0.5$
2. $\frac{3}{2}$
3. $5$
4. $\frac{2}{3}$

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

Q. In case of a compound microscope, an angular magnification of $30X$ is to be achieved using an eyepiece of focal length $5\text{cm}$ and an objective lens. Find the magnifying power of objective lens if the angular magnification is achieved in case of normal adjustment.

1. $7$
2. $9$
3. $8$
4. $6$

Q. A simple microscope using a single lens often shows coloured image of a white source. Why?

Q. The magnifying power of a compound microscope does not depend upon -

1. None of the above
2. tube length of the compound microscope.
3. the focal length of the eyepiece.
4. the aperture of the objective lens.

Q. The near point and the far point of a child are at 10 cm and 100 cm. If the retina is 2.0 cm behind the eye-lens, what is the range of the power of the eye-lens?

Q. The magnifying power of a microscope with an objective of 5 mm focal length is 400. The length of its tube is 20 cm. Then the focal length of the eye-piece is (consider that final image is formed at infinity)

1. 200 cm
2. 160 cm
3. 2.5 cm
4. 0.1 cm