A beam of light is incident at 60° to a plane surface. The reflected and refracted rays are perpendicular to each other. What is the R.I. of the surface:
1.1√3
2.√3
3.1/3
4.3
A blue cross on the white background is illuminated with white light and is observed through red filter. What is seen?
1.A red cross on a black background
2.A blue cross on a red background
3.A red cross on a blue background
4. A black cross on a red background
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?
1. 3D
2.1D
3.4D
4.2D
A convergent lens will become less convergent in :
1.oil
2.water
3.both of (a) and (b)
4.None of the above
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:
1. become zero
2.become infinite
3.reduce
4.increase
A double convex air bubble in water behaves as:
1. Convergent lens
2.divergent lens
3.plane slab
4.concave mirror
A point object is placed at the centre of a glass sphere of radius 6 cm 3 and RI = 32. The distance of virtual image from the surface of the sphere is :
1. 2 cm
2. 4 cm
3.6 cm
4.12 cm
A ray of light travelling in air is incident of a glass slab. The ray gets partly reflected and partly refracted. The phase difference between the reflected and the refracted waves is :
1. π/2
2.Ï€/4
3.Ï€
4.Zero
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:
1.5 mm
2.5 cm
3.0.5 m
4.5 m
A thin glass (RI = 32) lens has optical power of – 5D in air. Its optical power in a liquid medium with RI = 1.6 will be:
1.-2.5 D
2.25 D
3.-ID
4. 0.625 D
ar point of a myopic eye is 40 cm. The dioptic power of a corrective lens is:
1. 40 D
2.-4 D
3.-2.5 D
4.-0.25 diopter
If a mirror is approaching you at a speed of 10 ms^1, the speed with which your image approach you is:
1.10 ms-1
2. 5 ms-1
3.20 ms-1
4.15 ms-1
On reflection from a denser medium, a light wave suffers a phase difference of:
1. π
2.Ï€/2
3.Ï€/4
4.2Ï€
Radio waves from an antenna travel with the velocity of:
1.light
2.sound
3.ultrasonics
4.supersonics
The air bubble inside water shine due to:
1.Reflection
2.Refraction
3. T.l.R.
4.None of the above
The angle of deviation for a prism is greatest for:
1.violet
2.red
3.orange
4.yellow
The angle of minimum deviation for an equilateral glass prism is 30°. Refractive index of the prism is:
1. 1√3
2.√2
3.1
4.can’t be determined
The branch of optics dealing with the formation of images using the concept of straight line propagation of light is called:
1.geometrical optics
2. physical optics
3. corpuscular optics
4.quantum optics
The phase difference between the electric and the magnetic field vectors in electromagnetic waves is
1.Ï€/4
2.Ï€/2
3.Ï€
4.Zero
The refractive indices (R.I.) of glass and water with respect to air are 3/2 and 4/3 respectively. The R.I. of glass w.r. to w ater is:
1.8/9
2.9/8
3.7/6
4.2
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:
1.0°
2.30°
3.45°
4.60°
Two lens of power -15 D and +5 D are placed in contact co-axially. The focal length of equivalent lens is:
1.-10 cm
2.-20 cm
3.+10 cm
4.None
Two points P and q are situated at the same distance from a source of light but on opposite sides. The plane difference between the light waves passing through P and q will be:
1. n
2.2n
3.Ï€/2
4.zero
Two thin lenses of focal lengths 20 cm and 25 cm are placed in contact. The effective power of the combination is:
1.45 D
2.9 D
3.19 D
4. 6 D
When a beam of light is used to determine the position of an object, the maximum accuracy is achieved if the light is :
1.polarized
2. of longer λ
3.of shorter λ
4.of high intensity
When a ray of light (white) enters a lens, undergoes a change is:
1.wavelength
2.velocity
3.frequency
4.both velocity and wavelength
When light travels from one medium to another, which of the following does not change?
1. frequency
2.refractive index
3.velocity
4.wavelength
Which of the following cannot be polarised?
1.radiowaves
2.transverse waves
3.sound waves
4.X rays
Which of the following is not essential for the formation of a pure spectrum?
1.parallel beam of light
2.narrow beam of light
3.screen
4.prism in the minimum deviation position
Which of-the following is not a property of light?
1.It can travel through vacuum
2.It has a finite speed
3.It requires a material medium for its propagation
4.It involve transportation energy
Which produces additional luminiscence in a fluorescent tube?
1. infra red rays
2.ultraviolet rays
3.micro waves
4.radio waves