Compound Microscope

Q.

A compound microscope consists of an objective lens of focal length 2.0 cm and an eyepiece of focal length 6.25 cm separated by a distance of 15 cm. How far from the objective should an object be placed in order to obtain the final image at (a) the least distance of distinct vision (25 cm), and (b) at infinity? What is the magnifying power of the microscope in each case?

Q. A tank is filled with water to a height of $12.5\text{cm}$. The apparent depth of a needle lying at the bottom of the tank is measured by a microscope to be $9.4\text{cm}$. What is the refractive index of water? If water is replaced by a liquid of refractive index 1.63 up to the same height, by what distance would the microscope have to be moved to focus on the needle again?

Q. The focal lengths of the objective and eye-lens of a microscope are 1 cm and 5 cm respectively. If the magnifying power for the relaxed eye is 45, then the length of the tube is

1. 30 cm
2. 15 cm
3. 25 cm
4. 12 cm
   

Q. The focal length of objective and eye lens of a microscope are 4 cm and 8 cm respectively. If the least distance of distinct vision is 24 cm and object distance is 4.5 cm from the objective lens, then the magnifying power of the microscope will be

1. 18

2. 32
3. 64
4. 20

Q. The length of the compound microscope is 14 cm. The magnifying power for relaxed eye is 25. If the focal length of eye lens is 5 cm, then the object distance for objective lens will be

1. 1.8 cm

2. 1.5 cm

3. 2.1 cm

4. 2.4 cm

Q.

A square wire of side 3cm is placed 25 cm away from a concave mirror of focal length 10 cm. What is the area enclosed by the image of the wire? The center of the square lies on the principal axis and perpendicular to the axis.

Q.

A small telescope has an objective lens of focal length 144 cm and an eyepiece of focal length 6.0 cm. What is the magnifying power of the telescope? What is the separation between the objective and the eyepiece?

Q.

If the focal length of objective and eye lens are 1.2 cm and 3 cm respectively

and the object is put 1.25 cm away from the objective lens and the final

image is formed at infinity. The magnifying power of the microscope is

1. 200

2. 400

3. 250

4. 150

Q. The focal lengths of the objective and the eyepiece of a compound microscope are $2.0$ cm and $3.0$ cm, respectively. The distance between the objective and the eyepiece is $15.0$ cm, The final image formed by the eyepiece is at infinity. The two lenses are thin. The distance(in cm) of the object and the image produced by the objective, measured from the objective lens are respectively.

1. $2.4$ and $12.0$
2. $2.4$ and $15.0$
3. $2.0$ and $12.0$
4. $2.0$ and $3.0$

Q. A mark is made on the bottom of a beaker and a microscope is focused on it . The microscope is raised through 1.5 cm . To what height water must be poured into the beaker to bring the mark again into focus ? Given that 'n' is 4/3

Q.

A person with a normal near point (25 cm) using a compound microscope with objective of focal length 8.0 mm and an eyepiece of focal length 2.5 cm can bring an object placed at 9.0 mm from the objective in sharp focus. What is the separation between the two lenses? Calculate the magnifying power of the microscope,

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

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.

A far-sighted person can see objects beyond 71 cm clearly, if the separation between glasses and eye lens is 2 cm, then find the focal length of the glass?

Q. 55.The focal length of the objective and eyepiece of a compound microscope are 4cm and 6cm.respectively.if object is placed at a distance 6 cm in front of objective lens.the maximum magnification of microscope is

Q.

Differentiate between electron microscope and
optical microscope.

Q. A compound microscope is used to enlarge an object kept at a distance 0.03m from it’s objective which consists of several convex lenses in contact and has focal length 0.02m. If a lens of focal length 0.1m is removed from the objective, then by what distance the eye-piece of the microscope must be moved to refocus the image

1. 2.5 cm
2. 6 cm
3. 9 cm
4. 15 cm

Q. The focal length of the objective of a compound microscope is

1. greater than the focal length of eye piece
2. equal to the focal length of the eye piece
3. any of (a) (b) and (c)
4. lesser than the focal length of the eye piece

Q.

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

1. Increases

2. Does not change

3. May decrease or increase
4. Decreases

Q. Consider the statements.

1. The limit of resolution of a microscope can be decreased by filling a liquid of high refractive index between object and the objective lens.
2. Resolving power is inversely proportional to wavelength $\lambda$.

Choose the correct statements.

1. (1) only
2. (2) only
3. Both (1) and (2)
4. Neither (1) nor (2)

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. The magnifying power of the objective lens of a compound microscope is $7$. If the magnifying power of the compound microscope is $35$, then the magnifying power of the eyepiece will be -

1. $4$
2. $5$
3. $6$
4. $7$

Q. A compound microscope having $f_0=7\text{mm}$, $f_e=20\text{mm}$ and distance between the lenses is $20\text{cm}$. If image is formed at least distance of distinct vision then magnifying power? Answer the magnitude of nearest integer.

Q. 13. In a ramsdens eyepiece of effective focal length 4cm the focal length of the eye lens is

Q.

The image obtained by using a simple microscope is

1. real, erect and magnified

2. virtual, erect and magnified

3. virtual, inverted and magnified

4. real, inverted and magnified

Q.

In a compound microscope, if the objective produces an image $I_o$ and the eye piece produces an image $I_e$, then

1. I_o is virtual but I_e is real

2. I_o is real but I_e is virtual

3. I_o and I_e are both virtual

4. I_o and I_e are both real

Q.

A concave mirror of focal length $f$ forms an erect image twice the size of the object. Find the object distance from the mirror.

Q.

A compound microscope consists of an objective lens of focal length $1cm$ and an eyepiece of focal length $5cm$ with a separation of $10cm$. The distance between an object and the objective lens, at which the strain on the eye is minimum is $\frac{n}{40}cm$. The value of $n$ is

Q. A compound microscope has a magnification 30. The focal length of eyepiece is 5 cm. Assuming that the final image is formed at least distance of distinct vision (25 cm). Find the magnification produced by objective.

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?