Radio waves from an antenna travel with the velocity of:
  • light
  • sound
  • ultrasonics
  • supersonics
A point object is placed at the centre of a glass sphere of radius 6 cm 3 and RI = \(\frac{3}{2}\). The distance of virtual image from the surface of the sphere is :
  • 2 cm
  • 4 cm
  • 6 cm
  • 12 cm
The RI. of the material of a prism is √2 and its refracting angle is 30°. One of the refracting surface of the prism is made a mirror. A beam of monochromatic light entering the prism from the other face retraces its path, after reflection from mirror surface. The angle of incidence on prism is:
  • 0°
  • 30°
  • 45°
  • 60°
A telescope has an objective lens of 10 cm diameter and is situated at a distance of 1 km from two objects. The minimum distance between these two objects, which can be resolved by the telescope, when seen in the light of mean λ = 5000 A is of the order of:
  • 5 mm
  • 5 cm
  • 0.5 m
  • 5 m
When a beam of light is used to determine the position of an object, the maximum accuracy is achieved if the light is :
  • polarized
  • of longer λ
  • of shorter λ
  • of high intensity
A convex lens is dipped in a liquid, whose R.I. is equal to that of R.I. of material of the lens. Then its focal length will:
  • become zero
  • become infinite
  • reduce
  • increase
The velocity of light in vacuum is 3 × 1010 cms-1. The velocity of light in a medium (µ = 1.5) is:
  • 2 × 1010cms-1
  • 4.5 × 1010cms-1
  • 1.5 × 1010cms-1
  • None of these
Which of the following is not essential for the formation of a pure spectrum?
  • parallel beam of light
  • narrow beam of light
  • screen
  • prism in the minimum deviation position
A certain far-sighted person cannot see objects closer to the eye than 100 cm. The power of the lens which will enable him to read at a distance of 25 cm will be?
  • 3D
  • 1D
  • 4D
  • 2D
Which produces additional luminiscence in a fluorescent tube?
  • infra red rays
  • ultraviolet rays
  • micro waves
  • radio waves
For achromatic combination of lenses, if we use two lenses of focal length f' and f1 dipersive power to ω and ω' respectively, then
  • ω = ω0, ω'= 2ω0, f' = 2f
  • ω = ω0, ω' = 2ω0, f' = -2f
  • ω = ω0, ω' = 2ω0, f' = f/2
  • ω = ω0, ω' = 2ω0, f' = -f/2
ar point of a myopic eye is 40 cm. The dioptic power of a corrective lens is:
  • 40 D
  • -4 D
  • -2.5 D
  • -0.25 diopter
Two thin lenses of focal lengths 20 cm and 25 cm are placed in contact. The effective power of the combination is:
  • 45 D
  • 9 D
  • \(\frac{1}{9}\) D
  • 6 D
A blue cross on the white background is illuminated with white light and is observed through red filter. What is seen?
  • A red cross on a black background
  • A blue cross on a red background
  • A red cross on a blue background
  • A black cross on a red background
The angle of deviation for a prism is greatest for:
  • violet
  • red
  • orange
  • yellow
A double convex air bubble in water behaves as:
  • Convergent lens
  • divergent lens
  • plane slab
  • concave mirror
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