ICS Part 1 Physics English Medium Chapter 10 Online Short Questions Test with Answers

A telescope is made an objective of focal length 20 cm and eye-piece of 5 cm, both convex lenses. Find the magnifying power of telescope.

• Ans 1:

What do you mean by "Normal adjustment " in an astronomical telescope?

• Ans 1: In normal adjustment, the image formed by the objective lies at the focus of both the objective and the eye-piece and the final image appears to be formed at infinity. The distance between the objective and eye-piece of a telescope in normal adjustment is f_o+f_{e which equals the length of the telescope.}

How the power is lost in Optical fibre?

• Ans 1: If light is not perfectly monochromatic, power is lost due to dispersion (or spreading of the light signal). Some light is absorbed due to impurities in the glass. Some light is scattered by groups of atoms which are formed at places such as joints when fibres are joined together.

What is the near point? Give its numerical value?

• Ans 1: The minimum distance from the eye at which an object appears to be distinct is called near point or least distance of distinct vision.
  Its numerical value is 25 cm
  The location of the near point, however , change with age.

A magnifying glass gives a five time enlarged image at a distance of 25 cm from the lens. What will be the focal length of the lens?

• Ans 1:

• Ans 1:

One can buy a cheap microscope for used by the children. The image seen in such a microscope has coloured edges.Why is this so?

• Ans 1: It is due to the defects of lenses known a chromatic aberrations. This is because of the prism like formation of the lens which causes dispersion of white light.

What is the function of collimator in a spectrometer?

• Ans 1: Collimator is used to make the light rays parallel. It consists of a fixed metallic tube, a convex lens and an adjustable slit.

Define Magnification.

• Ans 1: The size of the object goes on increasing, when the object brought from a far off point to the focus of the lens. This phenomenon of enlargement is called magnification. Its is the ration of size of image to the size of object.

What is spectrometer?

• Ans 1: Spectrometer is a device which is used to study the spectra from different light sources.
  Its main parts are
  1. Collimator
  2. Turntable
  3. Telescope

  
  

What is resolving power in optical instrument? Write formula for grating.

• Ans 1:

Differentiate between microscope and telescope.

• Ans 1: Microscope is a device which is used to see the magnified image of very small and near object. Whereas telescope is an optical instrument used for viewing distant objects.

Why would it be advantageous to use blue light with a compound microscope?

• Ans 1:

What do you understand by linear magnification and angular magnification?Explain how a convex lens is used as magnifier ?

• Ans 1: Linear Magnification: is the ratio of the size of the image to the size of object.
  Angular Magnification: is the ratio of the angle subtended by the image as seen through the optical device to that subtended by the object at the naked eye placed at near point
  A convex lens of shorter focal length can be used as a magnifier when the object is placed very close to it.i.e When it lies between the lens and its focus.The image then formed is virtual, erect and magnified.

Differentiate between multimode step index and multimode graded index fibre.

• Ans 1:
• Ans 2:

What are different types of optical fibre?

• Ans 1: There are three types of optical fibres.
  1. Single mode step index fibre.
  2. Multimode step index fibre.
  3. Multimode graded index fibre.

What are uses of spectrometer?

• Ans 1: It is used to study spectra from different sources of light. Determine the wavelength of light by grating. Study the deviation of light by glass prism.
  Calculate refractive index of prism material

How the power is lost in Optical fibre?

• Ans 1: If light is not perfectly monochromatic, power is lost due to dispersion (or spreading of the light signal). Some light is absorbed due to impurities in the glass. Some light is scattered by groups of atoms which are formed at places such as joints when fibres are joined together.

What do you mean by "Normal adjustment " in an astronomical telescope?

• Ans 1: In normal adjustment, the image formed by the objective lies at the focus of both the objective and the eye-piece and the final image appears to be formed at infinity. The distance between the objective and eye-piece of a telescope in normal adjustment is f_o+f_{e which equals the length of the telescope.}

If the person was looking through a telescope at thee full moon, how would the appearance of the moon be changed by covering half of the objective lens?

• Ans 1: How will see the full moon still but the brightness will be reduced because less light is transmitting through the half covered lens.

How Convex Lens act as magnifying glass?

• Ans 1: A convex lens of shorter focal length can be used as a magnifier when the object is placed very close to it I.e. When it lies between the lens and its focus. The image then formed is virtual, erect and magnified.

Write the advantages of using light as transmission carrier wave over radio wave carriers.

• Ans 1: The use of light as transmission carrier wave in fibre optics gas several advantages over radio wave carriers such as a much wider bandwidth capability and immunity from electromagnetic interference.

What are different types of optical fibre?

• Ans 1: There are three types of optical fibres.
  1. Single mode step index fibre.
  2. Multimode step index fibre.
  3. Multimode graded index fibre.

What is resolving power in optical instrument? Write formula for grating.

• Ans 1:

Define Snell's law and write its mathematical form.

• Ans 1: Snell's law states that the ratio of the sines of the angles of incidence and refraction of a wave are constant when it passes between two given media. OR Snell' Law is a formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves passing through a boundary between two different isotropic media such as water, glass, or air.

A telescope is made an objective of focal length 20 cm and eye-piece of 5 cm, both convex lenses. Find the magnifying power of telescope.

• Ans 1:

• Ans 1:

What do you understand by Linear Magnification?

• Ans 1: Linear magnification is the ratio of the size of the image to the size of object.Angular magnification is the ratio of the angle subtended by the image as seen through the optical device to that subtended by the object at the naked eye placed at least distance of distinct vision.

Differentiate between microscope and telescope.

• Ans 1: Microscope is a device which is used to see the magnified image of very small and near object. Whereas telescope is an optical instrument used for viewing distant objects.

Why would it be advantageous to use blue light with a compound microscope?

• Ans 1: