300+ TOP Light Interview Questions [LATEST]

1. What Is Light ?

It is something we see and use everyday. Light is a form of energy. Light travels very fast. Light sometimes act as a wave, but unlike sound waves or water waves, it can travel through a vacuum.

2. What Is Difference Between Light Wave And Sound Wave ?

Light can travel through a vacuum but sound cannot travel through a vacuum.

3. Who First Suggested That The Light Is Neither Purely A Wave Nor Purely A Particle, But Has A Combination Of Both Properties ?

Max Plank. 

4. What Are Light Waves ?

The electromagnetic waves in nature are called light waves .

5. What Is Diffraction ?

It is the bending or spreading of light around tiny opaque objects.

6. What Is The Velocity Of Light In A Vacuum ?

3 * 10⁸

7. What Is Visible Light ?

It is the narrowest group in the electromagnetic spectrum.

8. Who Discovered The Photoelectric Effect ?

Heinrich Hertz

9. Who Put Forward The Theory Of Electromagnetic Radiation ?

Max Well, whose theory was substantiated by Heinrich.

10. Which Is The Source Of Electromagnetic Waves ?

The sun

11. What Depends On The Intensity Of Light ?

Amplitude

12. What Are Gamma Rays ?

They are very pentrating. They carry lots of energy and damage to living cells as they pass through.

13. Who Proved That The Light Travels Faster Than Sound ?

Olas Romer.

14. Which Gas Always Gives Out A Red Light ?

Neon, different gases produce different coloured light.

15. The Velocity Of Light Was First Measured By Whom ?

Olas Romer.

16. Colour Of Light Is Determined By?

Frequency

17. Who First Invented Electric Light Bulb ?

Thomas Alva Edison in 1879.

18. The Objects Start To Go Dull Red At About?

500 ⁰C 

19. What Changes Electrical Energy Into Light Energy ?

Light – emitting diodes ( LED )

20. Who First Explained How Light Is Reflected ?

The dutch physicist Hendrik Lorentz used James Clerk Maxwell’s theory of electro – magnetic waves to explain how light is reflected.

21. What Is Used To Collect The Light From Distant Stars ?

The optical telescopes.

22. What Is Refraction ?

Light travels in straight lines. But when it passes from one transparent material to another, the light rays bend. This is called refraction.

23. What Is Mirage ?

When light bends, it tricks us into seeing things in the wrong place. A mirage is caused by light reflection in the atmosphere. 

24. What Are The Uses Of Laser Light ?

They are used in eye surgery, surveying, cutting steel etc.

25. What Is Fluorescence ?

Some chemicals absorbs ultra violet light and that release energy as visible light. This is called fluorescence.

26. How Are Shadows Formed ?

Shadows are formed because light rays travel in straight lines and cannot bend around opaque objects in their path.

27. What Is Luminescence ?

It is the emission of light at low temperature. Fluorescence and phosphorescence are examples.

28. Which Is More Readily Seen At A Distance, A Plane Mirror Or A White Blotting Paper ?

A white blotting paper. Because the surface of white blotting paper is more diffusive than a plane mirror, hence, it scatters light in all directions. 

29. Why Fluorescent Tube Light Is Considered Better Than Tungsten Filament Bulb ?

Because, the efficiency of fluorescent tube is about 50 lumen / watt and whereas the efficiency of electric bulb is about 12 lumen / watt. Thus for the same amount of electric energy consumed, the tube gives nearly four energy consumed, the tube gives nearly four times more light than the filament bulb.

30. What Is Known As Coherent Sources ?

Two light sources which produces visible interfernce patterns with constant force are known as coherent sources.

31. What Happens To The Rest Of Energy In A Light Bulb Whose Efficiency Is So Low ?

The rest of energy is dissipated as heat.

32. Why Are Parabolic Mirrors Used In Search Light And Not Concave Spherical ?

Because a parabolic mirror is free from spherical aberrations. So a source of light placed at the focus of parabolic mirror produces a parallel beam of light which easily visible even from a long distance.

33. What Type Of Mirror Is Used By A Driver For Observing Traffic At The Back While Driving A Car Or Scooter And Why ?

A convex mirror, because it gives a virtual image smaller a size and hence wider view of traffic at the back. 

34. A Man Holding Alighted Candle In Front Of A Thick Glass Mirror And Viewing It Obliquely Sees A Number Of Images Of The Candles. What Is The Origin Of This Multiple Images ?

The front surface of a glass ( thick ) is both reflecting and refracting. The origin of these images is multiple reflection of light with in the glass by the front and back surfaces.

35. A Concave Mirror And Convex Lens Are Kept In Water. What Changes, If Any, Do You Except In The Focal Length Of Either ?

No change in the focal length of the concave mirror. It is half of its radius of curvature, no effect of external medium.

36. A Ray Of Light Is Incident Normally On The Glass Slab. What Will Be The Angle Of Refraction ?

The angle of refraction s zero.

37. The Surface Of The Sun Glasses Are Curved, Yet Their Power May Be Zero, Why ?

Both the surfaces of sun glasses are curved but parallel to each other. Therefore R 1 = R1

38. Who First Demonstrated The Phenomenon Of Interference Of Light With Help Of Double Slit ?

Thomas Young in 1801 

39. Does The Apparent Depth Of A Tank Of Water Change If Viewed Obliquely ? If, So Does The Apparent Depth, Increase Or Decrease ?

Yes, the apparent depth increases, when water tank viewed obliquely compared to the depth when seen near normally.

40. A Lens When Immersed In A Transparent Liquid Is Not Visible. Under What Condition Can It Happens ?

This can happen when refractive indices of two are equal. Under such conditions the lens material does not reflect any light and is not visible.

41. How Are The Three Different Mirrors Used ?

The plane mirror is used as working glass. The concave mirror is used for shaving as it gives magnified image of the face. The Doctors also use it to see the fine details of ear, nose, throat, etc. The convex mirror is used in automobiles. The mirror gives short images of the objects, thus enlarges the field of view.

42. Why Does Red Cloth Appear Black Under Green Light ?

The red cloth absorbs all light except red. Thus, when green light falls upon red cloth, it absorbs the greenlight and has nothing to reflect and thus, appears black.

43. Watching The Sunset On A Beach One Can See The Sun For Several Minutes After It Has Actually Set. Explain Why ?

This is due to refraction of light. 

44. How Would Blue Light Object Appear Under Sodium Lamp Light ?

Light from a sodium lamp is yellow. A blue object absorbs yellow light falling on it from the lamp. Therefore object will appear black.

45. What Is Newton’s Corpuscular Theory Of Light ?

According to newton particles are emitted by a source of light, and they travel in a straight line until the boundary of a new medium is encountered.

46. What Is The Nature Of Shaving Mirror ?

Concave mirror.

47. What Is The Nature Of Mirror Used By Dentist To Observe The Cavity In The Tooth Of Patient ?

Concave mirror

48. Which Feature Of Light Does Not Change When Light Goes From One Medium To Other ?

Frequency 

49. What Type Of Lens Like, Is An Air Bubble Inside Water ?

Concave lens, since water is denser than air.

50. A Bird Sees A Fish Inside A Pond Of Water. Is The Real Depth Of Fish More Or Less Than Apparent Depth ?

Apparent depth of fish according to bird is less than the real depth.

51. What Is Pure Spectrum ?

A spectrum in which there is no overlapping of colours.

52. What Is Impure Spectrum ?

A spectrum in which different colours overlap one another.

53. What Is Difference Between Spectroscope, Spectrograph And Spectrometer ?

Spectroscope is used for only observing a spectrum. In a spectrograph we can take photograph of the spectrum. In the a spectrometer, there is arrangement for making on measurements on the spectrum.

54. What Kind Of Spectrum Does A Candle Flame Give ?

A continuous emission spectrum.

55. What Is The Essential Condition For Observing A Rainbow ?

Back of observer must be towards sun.

56. Why Do We Prefer A Magnifying Glass Of Smaller Focal Length ?

Because magnifying power is more when focal length is short.

57. Objective Of A Compound Microscope Should Have A Small Focal Length. Why ?

To have larger magnifying power.

58. What Is The Sequuence Of Colours Observed In A Primary Rainbow ?

Inner edges violet and outer edges is red ( VIBGYOR )

59. What Angle Does The Radius Of Secondary Rainbow Subtend At The Observer’s Eye ?

52 ⁰

60. What Is Total Internal Reflection ?

Let light be going from a denser to a rarer medium. If angle to incidence is greater than the critical angle of incidence no light is refracted into the medium. The whole of light is reflected back into the first medium.

61. Which Are The Two Conditions For Total Internal Reflection ?

1.   Light must go from a denser to rare medium
2.   The angle of incidence must be more than critical angle of incidence.

62. Vechicles Moving In “ Foggy ” Weather Use Yellow Coloured Headlights. Why ?

In foggy weather scattering of light is large, becausse more scatters are present in the air. Wavelength of yellow light is large and intense yellow source are easy to produce. The yellow light will not undergo large scattering and will be observable from a long distance.

63. What Is Doppler Effect In Light ?

There is a change in the frequency of light radiation when the source or the observer move with respect to one another. This phenomenon is known as doppler effect.

64. What Is Shark Effect ?

The wavelength of light emitted by atoms is changed by the application of as strong transverse electric field to the source, the spectrum lines are split up into a number of sharply defined components. They are symmetrical about the position of the undisplaced line, and are proportional line, and are proportional to the field strength up to about 100,000 volts per cm.