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

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

• 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.

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 any two uses of spectrometer.

• Ans 1: It is used to study spectra from different sources of light.Its is used to determine the wavelength of light.

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

An astronomical telescope of long focal length and large aperture is considered to be a good telescope. Why?

• Ans 1: Objective of long focal length and large aperture is used to collect a great amount of light from the astronomical objects.

• 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.

Differentiate between multimode step index and multimode graded index fibre.

• Ans 1:
• Ans 2:

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.

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 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.}

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.

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

• Ans 1:

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:

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.

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.

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

• Ans 1:

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:

Define 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.

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.

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.

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 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.

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.

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

• Ans 1:

Differentiate between multimode step index and multimode graded index fibre.

• Ans 1:
• Ans 2:

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.

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.