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

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

• Ans 1:

Define total internal reflection and continuous refraction.

• Ans 1: Total Internal Reflection:When a light ray traveling from a denser medium towards a rare medium, makes an angle of incidence greater than critical angle of the medium, then the ray is totally reflected back into the same denser medium. This phenomenon is called total internal reflection.
  Continuous Refraction: It is the mode of propagation of light in which light is continuously refracted inside the different graded index fibers which are used in fibre optics.

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

Focal length of convex lens is 5 cm, calculate its magnification.

• Ans 1:

What are the problems having a high magnifying power in astronomical telescope?

• Ans 1: High magnifying power in astronomical telescope was accompanied by more spherical an chromatic aberration, geometric distortion and false colors.

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.

How light signals is transmitted through optical fibre?

• Ans 1: The lights signal are transmitted through the optical on the principle of
  • Total internal reflection
  • Continuous refraction

  In multimedia step index fiber, the signal is transmitted baby means of total internal reflection while in case of multimode graded index fiber, the signals transmitted by total internal reflection and continuous refraction.

What is the condition for total internal reflection?

• Ans 1: For glass- air boundary , when a propagating wave strikes the boundary at an angle larger than critical angle with respect to the normal to the surface, all the light is reflected and none is refracted to the air. This phenomenon is called total internal reflection. When a light ray travelling from a denser medium towards a rare medium, makes an angle of incidence greater than critical angle of the medium, then the ray is totally reflected back into the same denser medium.

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.}

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.

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:

How light signals is transmitted through optical fibre?

• Ans 1: The lights signal are transmitted through the optical on the principle of
  • Total internal reflection
  • Continuous refraction

  In multimedia step index fiber, the signal is transmitted baby means of total internal reflection while in case of multimode graded index fiber, the signals transmitted by total internal reflection and continuous refraction.

Why we use infrared light in a fiber optics communication system?

• Ans 1: Infrared light travels faster through optical fiber than visible light. So, it is preferred.

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.

When object lie within the principle focus of convex lens what is the nature of image and where it is formed?

• Ans 1: When object lie within the principle focus of convex lens, then image will be virtual, erect and magnified and will be formed at least distance of distinct vision.

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.

Find magnifying power of a convex lens of 25 cm focal length act as a magnifying glass.

• Ans 1:

Differentiate between multimode step index and multimode graded index fibre.

• Ans 1:
• Ans 2:

Define total internal reflection and continuous refraction.

• Ans 1: Total Internal Reflection:When a light ray traveling from a denser medium towards a rare medium, makes an angle of incidence greater than critical angle of the medium, then the ray is totally reflected back into the same denser medium. This phenomenon is called total internal reflection.
  Continuous Refraction: It is the mode of propagation of light in which light is continuously refracted inside the different graded index fibers which are used in fibre optics.

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.

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.

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

• Ans 1:

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.

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.

• Ans 1:

What is the condition for total internal reflection?

• Ans 1: For glass- air boundary , when a propagating wave strikes the boundary at an angle larger than critical angle with respect to the normal to the surface, all the light is reflected and none is refracted to the air. This phenomenon is called total internal reflection. When a light ray travelling from a denser medium towards a rare medium, makes an angle of incidence greater than critical angle of the medium, then the ray is totally reflected back into the same denser medium.

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.

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.

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.