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Very Short Answers
Question 1 Short answer type questions:
(i)What is the difference between luminous and non-luminous?
(ii)Explain the given term “Angle of Incidence”.
(iii)What is the regular reflection of light?
(iv)Name the colours present in the white light?
(v)Define Tactual aids. Answers
(i)Objects that can emit light energy by themselves are known as luminous object and objects that cannot emit light energy by themselves are known as non-luminous objects.
(ii)The angle of incidence is the angle between the normal and the incident ray.
(iii)When light falls on a smooth uniform surface, all the parallel incident rays are reflected perfectly parallel is known as regular reflection of light.
(iv)There are seven colours present in white light like, red, orange, yellow, green, blue, indigo, and violet.
(v)Tactual aids are non-optical sensory aids which involve the use of touch.
Multiple Choice Questions
Question 2 Multiple Choice Questions
(a) Which type of reflection shown by given figure:
(i)Angle of incidence
(ii)Regular and irregular
(ii)Law of reflection
(iv)Angle of reflection
(b)What is the value of $\theta$,if n=5?
(c)Which device is used to see things above the surface of the water?
(d)The light sensitive layers of nerve tissue at the back of the eye that receive images and sends them as electric signals through the optic nerve to the brain.
(e)What is the minimum distance which our normal eye can see distinctly?
(iv)All of the above Answers
There are two type of law of reflection:
(1) The incident ray, the reflected ray and the normal, all lie in the same plane.
(2) The angle of incidence is equal to the angle of reflection.
Explain the types of reflection? Answers
There are two type of reflection:
(1) Regular : In regular Reflection, light reflected from a smooth surface in a definite direction.
(2) Irregular: In irregular reflection, light reflected from a rough surface in all directions and not in a definite direction.
A kaleidoscope is an optical instrument consisting of two or more reflecting surfaces. These surfaces tilted towards each other at a certain angle to obtain symmetrical patterns when viewed from the other end.
Why Ambulance is written opposite on the Ambulance? Answers
Ambulance is written opposite on the Ambulance because of the lateral inversion property of mirrors. As the property describes, left becomes right and right becomes left. Therefore, if anyone sees the Ambulance in the mirror, it looks correct.
What is periscope? Write its uses. Answers
A periscope is a long, tabular device through which a person can see objects that are out of the direct line of sight. It is used in submarine navigation and in land and sea warfare.
Write the definition of power of accommodation. Answers
Power of accommodation is the ability of the eye lens to focus near and far objects clearly on the retina by adjusting its focal length.
What happens when we see a faraway object? Answers
When we see a faraway object, the ciliary muscles relax and flatten the lens so that its focal length increases. Thus, while seeing distant objects we never feel any strain on the eye.
What is cataract and how it affects the eye? Answers
Cataract is an eye disease generally occur at the old age. Sometimes due to the formation of a membrane over the crystalline lens of some people in the old age, the eye lens becomes hazy or even opaque. It results in decrease or loss in vision of the eye.
Long answer type questions:
Describe multiple reflection with the help of a suitable diagram. Answers
Place an object between the mirrors. You can see several images in both the mirror. This is because the image formed by one mirror acts as the object for the second mirror. This phenomenon is referred to as multiple reflections.
The no. of images formed depends on the angle between the mirrors. The formula used for finding the no. of images are $n= 360 \div \theta -1$ Where n is the no. of images and is the angle between the two mirrors.
Write a short note on Braille system. Answers
Braille is a system developed by Louis Braille in 1824 to help visually challenged people. It is a code by which languages such as English, French, Spanish, etc. can be written and read. This code consists of raised dots, that can be read with fingers by blind people. It is a widely used system across the globe and is a very important invention. Braille symbols are represented inside units of space known as Braille cells. A full cell consists of a set of six raised dots arranged in the form of a 2*3 matrices. 64 different combinations can be created by using one or more dots. Each cell is used to represent an alphabet, a number, a punctuation mark, or a special symbol.
This light class 8 Extra Questions is prepared keeping in mind the latest syllabus of CBSE . This has been designed in a way to improve the academic performance of the students. If you find mistakes , please do provide the feedback on the mail.
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