Simple Microscope Angular Magnification

Q.

What are three characteristics of laser?

Q.

In a compound microscope magnification will be large, if the focal length of the eye piece is

1. Equal to that of objective

2. Less than that of objective

3. Large

4. Smaller

Q. Difference between refracting type telescope and reflecting type telescope

Q.

When image is formed at infinity, what does it mean??

What we'll see?

Q.

An object is put at a distance 25 cm from the optical centre of a convex lens. If it's real image is formed at a distance 30 cm from the lens to its focal length is about

(1) 10 cm

(2) 14 cm

(3) 12 cm

(4) 20 cm

Q.

What is the full form of VDU in computer

Q.

A nearsighted man can clearly see objects up to a distance of 2m. Calculate the power of the lens of the spectacles necessary for the remedy of this defect.

Q. The objective of a telescope is of larger focal length and of larger aperture compared to eye piece. Why?give reasons

Q. In an electron microscope, the resolution that can be achieved is of the order of the wavelength of electrons used. To resolve a width of $7.5\times {10}^{-12}\text{m}$, the minimum electron energy required is close to

1. $1\text{keV}$
2. $25\text{keV}$
3. $500\text{keV}$
4. $100\text{keV}$

Q. An object is placed on the axis of a convex lens. Its real image is formed 80 cm from the object. The magnification is 3. The focal length of the lens is

Q. 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. The maximum magnifying powers if she uses the microscope (a) together with the glasses and (b) without the glasses are

1. 6, 6
2. 9, 6
3. 6, 9
4. 9, 9

Q.

State the differences between a convex and a concave lens.

Q. Figure given below shows a beam of light converging at point P. When a convex lens of focal length 16 cm is introduced in the path of the beam at a place O shown by dotted line, the beam converges at a distance x from the lens. The value x will be equal to

1. 12 cm
2. 24 cm
3. 36 cm
4. 48 cm

Q.

The magnifying power of a compound microscope increases when

1. The focal length of the objective lens is increased and that of the eyepiece is decreased

2. The focal length of the eyepiece is increased and that of the objective lens is decreased.

3. Focal lengths of both objective and eyepiece are increased.

4. Focal length of both objective and eyepiece are decreased.

Q. Answer the following questions: (a) The angle subtended at the eye by an object is equal to the angle subtended at the eye by the virtual image produced by a magnifying glass. In what sense then does a magnifying glass provide angular magnification? (b) In viewing through a magnifying glass, one usually positions one’s eyes very close to the lens. Does angular magnification change if the eye is moved back? (c) Magnifying power of a simple microscope is inversely proportional to the focal length of the lens. What then stops us from using a convex lens of smaller and smaller focal length and achieving greater and greater magnifying power? (d) Why must both the objective and the eyepiece of a compound microscope have short focal lengths? (e) When viewing through a compound microscope, our eyes should be positioned not on the eyepiece but a short distance away from it for best viewing. Why? How much should be that short distance between the eye and eyepiece?

Q.

A person uses a lens of power $+3D$ to normalize vision. Find the near point of the hypermetropic eye (in m).

Q.

If u aan v are the objobj and image distances respectively due to convex lens then which among the following statements is false

(1)as u increases, v also increases

(2)as u increases, v decreases

(3) as u increases v remare constant

(4)None of the above

Q.

A simple magnifying glass consists of a

1. concave lens

2. convex lens of large focal length

3. convex lens of small focal length

4. plane mirror only

Q.

How should people wearing spectacles work with a microscope?

1. They should keep on wearing their spectacles.

2. They should never use the microscope.

3. They should take off their spectacles.

4. They may either put on their spectacles or they may take off their spectacles.

Q. The numerical aperture of a microscope required to just resolve two points separated by a distance of ${10}^{-4}\text{cm}$ when wavelength of light is $5.8\times {10}^{-5}\text{cm}$ is

1. $3.5$
2. $0.035$
3. $0.35$
4. $35$

Q. The magnifying power of a simple microscope can be increased, if we use eye-piece of

1. Higher focal length

2. Smaller focal length

3. Higher diameter

4. Smaller diameter

Q. When an object is viewed using light of wavelength $6000\mathring{\text{A}}$ under a microscope, the resolving power of the microscope is ${10}^4$. Find the resolving power of the microscope, when the same object is viewed using light of wavelength $4000\mathring{\text{A}}$?

1. $1.5\times {10}^4$
2. $2\times {10}^4$
3. $3.2\times {10}^4$
4. $3\times {10}^4$

Q.

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

Q. An astronomical telescope has objective and eyepiece of focal lengths $40\text{cm}$ and $4\text{cm}$ respectively. To view an object $200\text{cm}$ away from the objective, the lenses must be separated by a distance of-

1. $37.3\text{cm}$
2. $46.0\text{cm}$
3. $50.0\text{cm}$
4. $53.4\text{cm}$

Q.

Consider a beam expander which consists of two converging lenses of focal lengths $40\mathrm{cm}$ and $100\mathrm{cm}$ having a common optical axis. A laser beam of diameter $2\mathrm{mm}$ is incident on the $40\mathrm{cm}$ focal length lens. Then what is the diameter (in mm) of the final beam (see figure)?

Q. An object is kept at a dis†an ce of 1 m from a convex lens of power 2 dioptre. The image is formed at a dis†an ce ______ from the object.

Q. converging beam of light forms a sharp image on a screen.A lens is placed 10 cm from the screen in the path of thebeam. It was found that the screen has to be moved 8 cmfurther away to obtain the sharp image. Focal length of the

Q.

Magnifying power of a simple microscope is (when final image is formed at D = 25 cm from eye)

[MP PET 1996; BVP 2003]

1. $\frac{D}{f}$
2. $1+\frac{D}{f}$
3. $1+\frac{f}{D}$
4. $1-\frac{D}{f}$

Q. A telescope has an objective of focal length 50 cm and eyepiece of focal length 5 cm. The least distance of distinct vision is 25 cm. The telescope is focussed for distinct vision on a scale 200 cm away from the objective. Calculate the magnitude of magnification produced.

Q.

Lenses are used to form images by reflection in optical instruments.

1. True
2. False