IMPORTANT QUESTION OF LIGHT FOR CBSE CLASS 10  

Chapter : Light Reflection and Refraction. 

 Q1. What is light? 

Ans: Light is a form of energy which provides sensation of sight. 

Q2. What kind of wave is light? 

Ans: Electromagnetic wave

Q3. Justify that light is an Electromagnetic wave with two reason. 

Ans: light is an Electromagnetic wave because-

i) It doesn't require any material medium for its propagation. 

ii) It travels with speed of 3×10^8m/s

iii) It consists of electric field and magnetic field oscillating perpendicular to each other. 

Q4. Is light transverse or longitudinal wave? 

Ans: Transverse wave. 

Q5.Which behavior does light shows? 

Ans : Light show dual behavior. 

i) wave nature and

ii) particle nature. 

Q6.What the tiny packets of light energy called? 

Ans: Photons. 

Q7. Name two phenomenon which prove light is a wave? 

Ans. Reflection., Refraction, interference ,diffraction, polarization (any two) . 

Q8. Name two phenomenon which support particle nature/ quantum nature of light. 

Ans: Photo electric effect. 

Get notes of English class 10 : Click Here

Q9.Write the characteristics of light

Ans. a)  light is an Electromagnetic wave

b) It doesn't require any matrial medium for its propagation. 

c) It always travels in straight line. 

d) It travels with speed of 3×10^8 m/s.

e) It shows dual behavior. 

Q10. Which characteristics of light doesn't change with change in medium. 

Ans. Frequency. 

Q11.Which characteristics of light decides its colour.? 

Ans. Wavelength. 

Q12. What are the conditions for seeing an object. 

Ans. i) there must be a source of light. 

ii) Light must fall onto the object and reflected. 

iii) Reflected light must enters observer eye. 

Q13. What is luminous object? 

Ans. The source of light which emits their own light is called Luminous object. 

Q14. Give some examples of luminous source of light. 

Ans. Stars, sun, candle, bulb etc. 

Q15. Give some examples of non luminous source of light. 

Ans. Moon, planet, chair, table, pen etc

Q16. Which colour of light has

 i) maximum wavelength. 

ii) minimum wavelength. 

iii) maximum frequency. 

iv) minimum frequency

Ans. i) Red

ii) Violet

iii) Violet

iv) Red

Q17. What do you mean by a ray of light.? 

Ans. A ray of light represent the direction of light represented by a single headed arrow. 

Q18. What is beam of light? 

Ans. A bundle of rays is called beam of light. 

Q19. What is Reflection of light? 

Ans. The phenomenon of bouncing back of light after striking a surface is called Reflection of Light. 

Q20. State the laws of Reflection. 

Ans. There are two laws of reflection

i) the incident ray, the reflected ray and the normal at the point of incidence all lies on the same plane. 

ii) Angle of incidence is always equal to the angle of reflection. 

     i,e.          <i = <r

Q21. Distinguish between regular reflection and diffuse reflection. 

Ans. Regular reflection:- the type of reflection in which the parallel incident rays remains parallel after reflection.  for example reflection by a smooth surface for mirror. 

Diffused reflection: type of reflection in which parallel incident ray not remains parallel after reflection for example reflection by a rough surface. 

Q22. Which type of reflection help us to see an object from any direction. ? 

Ans.  diffused reflection

Q23. What Will be the angle of reflection if a Ray of light incident normally to a mirror? 

Ans. Zero degree. 

Q24. Differentiate between real image and virtual image. 

Ans. 

Real image	Virtual image
1.Formed when rays of light actually meet at a point after reflection or refraction.	1.Formed when rays of light appears to meet at a point after reflection or refraction.
2.Can be obtained on screen.	2.Cannot be obtained on screen.
3. Images are inverted w.r.t. object.  Ex. Image formed by concave mirror and convex lens.	3.Images are erect w.r.t. object.  Ex. Images formed by plane mirror, convex mirror and concave lens.

Q25. Write the characteristics of images formed by plane mirror. 

Ans. Characteristics of images formed by plane mirror are-

1. Virtual and erect.

2. Same size as object. 

3. Same distance as object from the mirror

4. Laterally inverted.

Q26. Define center of curvature of a mirror. 

Ans. Centre of the hollow sphere of which spherical mirror is a part is called centre of curvature of the spherical mirror. Denoted as C. 

Q27. Define pole of a mirror. 

And. The center of actual reflecting surface of the mirror is called pole of the mirror. Denoted as P.

Q28. Define Radius of curvature of the mirror. 

Ans. Distance between pole and center of curvature of the mirror is called radius of curvature. 

Q29. Define principal focus of a mirror. 

Ans. The common point at which the rays incident parallel to principal axis meet of appear to meet after reflection is called principal focus of the mirror. 

Denoted as F. 

Q30. Define focal length of a mirror. 

Ans. The distance between pole and principal focus of a mirror is called focal length of the mirror. 

Denoted as f.

Q31. Define principal axis of a spherical mirror. 

Ans. A straight line joining the pole and centre of curvature of the mirror is called principal axis. 

Q32. Write the relation between focal length and radius of curvature. 

Ans.          f = R/2

      where, 

                   f = focal length

                   R=radius of curvature

Q33. What is focal length of a plane mirror. 

Ans. Infinite. 

Q34. What is the power of a plane mirror. 

Ans. Zero. 

Q35. What is the SI unit of power?

Ans. diopter (D)

Q36. Where should an object be placed in front of a convex lens to get a real image of the same size of the object?

Ans. At twice the focal length.