Light

Q63. Draw a diagram to show the reflection of light from a plane mirror. Label the following on the diagram: Incident ray, Reflected ray, Angle of reflection, Normal and Angle of incidence

Ans.

Image from NCERT

Q64. Differentiate between regular and diffused reflection. Does diffused reflection mean the failure of the laws of reflection?

Ans. Difference between regular and diffused reflection

Q65. Two mirrors meet at right angles. A ray of light is incident on one at an angle of 30° as shown in figure. Draw the reflected ray from the second mirror.

Ans.

Q66. What are the functions of the following parts of the eye?
Iris, Eye-lens, Retina and Optic nerve

Ans. Iris – Iris controls the size of the pupil. The iris is the part of that eye which gives it its distinctive colour.

Eye-lens - The lens focuses light on the back of the eye, on a layer called retina.

Retina - Retina receives the light focused by the lens. Retina contains several nerve cells. Sensations felt by the nerve cells are then transmitted to the brain.

Optic nerve - The job of the optic nerve is to transfer visual information from the retina to the brain.

Q67. Explain how you can take care of your eyes.

Ans. It is necessary that we take proper care of our eyes. If there is any problem we should go to an eye specialist. Have a regular checkup.

                          i.        If advised, we should use suitable spectacles.

                         ii.        Too little or too much light is bad for our eyes. Insufficient light causes eyestrain and headaches. Too much light, like that of the sun, a powerful lamp or a laser torch can injure the retina.

                         iii.        We should not look at the sun or a powerful light directly.

                         iv.        We should not rub our eyes. If something gets into the eyes, we should splash the eyes with a lot of clean water. If there is no improvement then we should consult a doctor.

                         v.        We should wash our eyes frequently with clean water.

                        vi.        We should always read at the normal distance for vision. We should not read by bringing our book too close to our eyes or keeping it too far.

Q68. (a) Find out the position of the image of an object situated at A in the plane mirror.
(b) Can Paheli at B see this image?
(c) Can Boojho at C see this image?
(d) When Paheli moves from B to C, where does the image of A move?

Ans.

(a)

(b) Yes, Paheli can see the image at B.

(c) Yes, Boojho can see the image at C.

(d) No, change of image A.