Class 8 Science Lesson 16 Inside Question and Answer NCERT & CBSE Board Here in this post. NCERT Class 8 Science Textbook Lesson 16 Inside Questions.
Grade: VIII
Lesson 16 Light
Que. 1) Fill in the blanks.
(1) Light is reflected from ——-
Ans-
(2) Diffused or irregular reflection takes place from —- surface.
Ans- rough
(3) Image formed in a plane mirror undergoes——-
Ans- lateral inversion.
(4) ——- called white light.
Ans- sunlight
(5) The most popular resource for visually challenges person is —–
And- Braille
Que. 2) answer the following question.
(1) Define the followings.
(a) Incident ray –The light ray, which strikes any surface, is called the incident ray.
(b) Reflected ray- The ray that comes back from the surface after reflection is known as the reflected ray.
(c ) Angle of incident-The angle between the normal and incident ray is called the angle of incident.
(d) Angle of refraction- The angle between the normal and the reflected ray is known as the angle of reflection.
(e) Regular reflection-The reflection from a smooth surface like that of a mirror is called Regular reflection.
(f) Blind spot- At the junction of the optic nerve and the retina , there are no sensory cells, so no vision is possible at that spot this is called the blind spot.
(2) What are the lateral inversion.
Ans- The image formed by a mirror on the left side and the object appears on the right and the right side object appears on the left. This is known as lateral inversion.
(3) Give two laws of reflection.
Ans-There are two laws of reflection –
- The angle of incident is always equal to the angle of reflection is known as the first law of reflection.
- The incident ray the normal at the point of incident and the reflected ray all lie in the same plane. This is known as the second law of reflection.
(4) Write short note on care of the eyes.
Ans- It is necessary that take proper care of eyes. If there is any problem we should go to an eye specialist. Some are the followings things we should avoid-
- Too little and too much light is bad for eyes. Insufficient light causes eyestrain and headaches. So use of mobile phone adjusting the brightness.
- Too much light like that of the sun a powerful lamp or a lesser or torch can injure the retina. So use goggles at sun light.
- Do not look at the sun or a powerful light directly.
- Never rub our eyes. If particles of dust go into our eyes, wash our eyes with clean water. If there is no improvement go to a doctor.
- Always read at the normal distances for vision. Do not read by brining the book too close to our eyes or keeping it too far.
- This is do for taking care of eyes.
(5) What is the Braille system?
Ans- Braille system is developed for the person who is visually challenged. Louis Braille himself a visually challenged person. He developed a system for visually challenged persons and published it in 1821. Many Indian languages can be read using the Braille system.
Braille system has 63 dot patterns or characters. Each character represent a letter a combination of letters , a common word or a grammatical sign. Dots are arranged in cells of two vertical rows of three dots each. Patterns of dots to re[present some English letters. This patterns helps visually challenged persons to recognize words by touching.
(6) What are luminous objects.
Ans- There are some objects which give their own light like Sun, fire, flame of candle and an electric lamp. Their light falls on our eyes. The objects which emit their own light are known as Luminous objects.