Q1. What is meant by 'incident ray'?
Ans: - The ray of light which falls on the mirror surface is called incident ray.
Q2. What is meant by 'reflected ray'?
Ans: - The ray that comes back from the surface after reflection is known as the reflected ray.
Q3. How many reflected rays can there be for a given single incident ray falling on a plane mirror?
Ans: - There can be only one reflected ray
Q4. What do you understand by the term 'point of incedence'?
Ans: - The place where all Incident ray, normal, reflected ray meet is called point of incidence.
Q5. What is 'normal' in the reflection of light from a plane mirror?
Ans: - Perpendicular at the point of incidence is known as normal.
Q6. Define angle of incidence?
Ans: - The angle between normal and incident ray is called angle of incidence.
Q7. Define angle of reflection?
Ans: - The angle between normal and reflected ray is called angle of reflection.
Q8. A ray of light is incident on a plane mirror at an angle of 30°. What is the angle of reflection?
Ans: - 30°
Q9. An incident ray makes an angle of 75° with the surface of plane mirror. What will be angle of reflection?
Ans: -
75° + x = 90°
x = 90° - 75° = 15°
∴ 15° is the angle of reflection
Q10. A ray of light is incident normally (perpendicularly) on a plane mirror. Where will this ray of light go after reflection from the mirror?
Ans: - The ray reflects and follows the same path.
Q11. What is the angle of incidence when a ray of light is incident normally on a plane mirror?
Ans: - 0°
Q12. What is the angle of reflection when a ray of light normally on a plane mirror?
Ans: - 0°
Q13. What is the angle of incidence of a ray of light if the reflected ray is at an angle of 90° to the incident ray?
Ans: - 45°
Q14. Name the apparatus which is used to obtain a thin beam of light.
Ans: - Ray box
Q15. What type of reflection of light take place from:
(a) a rough surface?
(b) a smooth surface?
Ans: -
(a) Diffused or Irregular reflection
(b) Regular reflections
Q16. Which type of reflection of light, regular reflection or diffused reflection, leads to the formation of images?
Ans: - Regular reflection
Q17. What type of reflection of light takes place from:
(a) a cinema screen?
(b) a plane mirror?
Ans: -
(a) Diffused Reflection
(b) Regular Reflection
Q18. If an object is placed at a distance of 7.5 cm from a plane mirror, how far would it be from its image?
Ans: - 7.5 + 7.5 = 15.0
Distance between image and object is 15 cm.
Q19. Is the image of an object in a plane mirror virtual or real?
Ans: - Virtual
Q20. Name the phenomenon resposible for the following effect:
When we sit in fornt of a plane mirror and write ith our right hand, it appears in the mirror that we are writing with our left hand.
Ans: - This phenomenon is called laterial inversion
Q21. Name a device which works on the reflection of reflected light.
Ans: - Periscope
Q22. How are two plane mirrors in periscope arranged:
(a) with respect to another?
(b) with respect to sides of tube?
Ans: -
(a) Parallel - with respect to another
(b) at 45° - with respect to sides of tube
Q23. What will be the number of images formed when an object is placed between two parallel plane mirrors facing each other?
Ans: - Infinite
Q24. Name an instrument or toy which works by producing multiple reflections from three plane mirrors to form beautiful patterns.
Ans: - Kaleiodoscope
Q25. State one use of kaleiodoscope
Ans: - Kaleidoscope are used by designers of wall papers and fabrics, as well as by artists to get ideas for new ideas of new patterns.
Q26. Name the device used to split white light into seven colours.
Ans: - Glass Prism
Q27. What happens when a beam of sunlight is passed through a glass prism?
Ans: - Th white light spreads into seven colours.
Q28. What type of lens (convex or concave) is present in the human eye?
Ans: - Convex lens
Q29. What is the range of vision of a normal eye?
Ans: - Infinity
Q30. Name the point inside the human eye where the image is not visible.
Ans: - Blind Spot
Q31. Name the phenomenon which enables us to see movies in a cinema hall.
Ans: - Persistence of vision
Q32. Name an eye ailment (ot eye-disease) caused by the deficiency of Vitamin A in the diet.
Ans: - Night Blindness
Q33. What is the name of transparent front part of eye?
Ans: - Cornea
Q34. What is the small opening in the iris of an eye?
Ans: - Pupil
Q35. Which part of eye gives it its distincitve colour?
Ans: - Iris
Q36. Write the names of the main parts of the human eye?
Ans: - Cornea, Iris, Pupil, Ciliary muscles, Eye lens, Retina, Blind spot, Optic nerve
Q37. What happens to the size of the pupil of our eye in dim light?
Ans: - Enlarges
Q38. What happens to the size of the pupil of our eye in bright light?
Ans: - Gets smaller
Q39. State whether the following statements are True or False:
(a) The moon is an illuminated object.
(b) Diffuse reflection means the failure of the laws of reflection of light.
(c) In a kaleeidoscope, a pattern seen once can never be seen.
Ans: -
(a) True
(b) False
(c) True
Q40. Fill in the following blanks with suitable words:
(a) The angle of ________ equals the angle of reflection.
(b) A person 1m in front of a plane mirror seems to be ______m away from his image.
(c) If your ____ ear with right hand in front of a plane mirror, it will be seen in the mirror that your right ear is touched with ________.
(d) The size of pupil becomes _______ smaller when you see dim light.
(e) Night birds have ____ cones than rods in their eye.
(f) The image of an object persists on the retina of an eye for about _____ second even after the object has disappered.
(g) If the still pictures of a moving object are flased on our eyes at a rate faster than _______ pictures per second, the eye perceives object as oving.
(h) In a movie, the sill pictures in a proper sequence are projected on the screen usually at the rate of ______ pictures per second.
Ans: -
(a) incidence
(b) 1
(c) left; left hand
(d) enlarges
(e) less
(f) 1⁄16 th of a second
(g) 16 pictures per second
(h) 24 pictures per second
