Chhattisgarh State Board Class 10 Science Chapter 10 Light: Reflection and Refraction from Plane Exercise Multiple Choice, Fill in the Blanks, Questions and Answers here.
Chhattisgarh State Class 10 Science Chapter 10 Solution
1) Choose the correct answer–
(i) If we rotate a plane mirror by 2Q, then the reflected ray will rotate by–
(a) 2Q (b) 3Q (c) 4Q (d) Q.
Ans: – (c) 4Q.
(ii) What should be the minimum length of the plane mirror if a person wants to see hisfull image?
(a) One fourth of the person’s height.
(b) One third of the person’s height
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(c) equal to the person’s height.
(d) One half of the person’s height.
Ans: – (d)
(iii) How many images will be formed of an object kept between two mirrors making 45°with eachother?
a) 5 (b) 6 (c) 7 (d) 8.
Ans: – (c) 7.
(iv) If an object is placed at a distance of 3 cm from the mirror, then the distance betweenthe image and the object will be–
a) 4 cm (b) 6 cm (c) 3 cm (d) 12 cm.
Ans: – (b) 6 cm.
2) Fill in the blanks
(i) Image formed by a plane mirror is erect, virtualand………same size…………………………
(ii) Second law of refraction is also known as……………………..Snell law……………………….
(iii) Light ray falls normally on plane mirror; the angle of reflection will be……….zero……….
(iv) For……. bending away from normal …………………..light should travel from denser medium to rarer medium.
3) What are the laws of reflection?
Ans: – As we know there are two laws of reflection which are – (i) The incident ray, reflected ray and the normal to the plane of the mirror always remain in the same plane.
(ii) The angle of incidence and angle of reflection always be same with respect to the normal.
4) What are the laws of refraction?
Ans: – The ratio of the sine angle of incidence and reflection rays is the ratio of the velocity of these two media.
Or, Sini / Sinr = Va / Vb;
5) The refractive indices of medium A and B are nAand nB respectively. Total internal reflectionis possible on-going form which medium to which medium given that nA> nB.
Ans:- The total internal reflection always happens when a light ray transforms from the denser to rarer medium. In this nA > nB so we can say that the density of the medium A is more than the medium B. So, the light should transfer from the medium A to medium B.
6) What is total internal refraction and what are the necessary conditions for it to take place?
Ans: – when the light rays pass from denser to rarer medium then if the angle of incidence is grater than the critical angle then light ray bend comparing to the normal line this phenomenon is known as the total internal reflection.
For the total internal reflection, the light rays must be passes through the denser medium to the rarer medium.
7) Give two examples where refraction is seen in daily life.
Ans: – The mirror and ice are the common example of the refraction of the light rays seen in daily life.
8) What do you understand by critical angle?
Ans: – The critical angle is formed when the angle of refraction is more than the 90° . For example, the critical angle of the water 48° tells us that if any rays go from water to another object by this angle, then it doesn’t come back.
10) Refractive index of diamond is 2.42. Explain this statement.
Ans: – The refractive index 2.42 tells us that ratio of the speed of light in vacuum to the speed of light in that medium is the same value as this.
11) A light ray travelling in the air enters the Ice. Will the light ray move away from the normal or towards the normal? Why?
Ans: – When the light is traveling in the air enters to the ice the light ray will bend towards the normal of the ice. As we all know that light rays when passes through the rarer to denser medium always bend towards the normal line.
12) If we increase the distance between the mirror the object then what would be the effect on the distance between the image and the object?
Ans: – If we increase the distance between the mirror then the distance between the object and the image will be increased as we increase the distance.
13) What is the difference between virtual image and real image?
Ans: –
| Virtual image | Real image |
| Image is formed when rays are divergence. | Image is formed when rays are convergence. |
| Example: – The reflection mirrors show this image. | Example:- cinema mirror. |
14) What is the difference between absolute refractive index of a medium and the relative refractive index of two mediums? What is the relation between them?
Ans: –
|
Absolute refractive index |
Relative refractive index |
| The absolute refractive index is the ratio of speed in vacuum to the medium of the light rays. | Relative refractive index is the ratio between the sped of light of two medium. |
| Its value comparatively more. | Its value comparatively less to absolute refractive index. |
The relation between this index is,
Retroactive index respect to air = (Absolute refractive index /relative refractive index).
15) What is the principal of reversibility?
Ans: – When a beam of light is falling on an object by any reason if the direction of the ray’s reverses, then the light rays will go back in the same direction as we as same path after the reverse.
16) State the reasons for following: –
(i) The position of fish in a pond is not same as it is observed from outside.
(ii) A Bubble of air shines in water.
(iii) Mirage is an illusion.
Ans: –
a) The position of the fish is not same as we see it from the upper side of the water. It actually in more depth as compare to the previous position because of the refractive index of the air and water we see this phenomenon.
b) The air bubbles present in the air shines in water because the bubble surface show’s the total internal reflection. As we all know for the total internal reflection the rays bend away from the normal line.
Mirage is seen in the desert area mostly in that although we see a water source but in real situation its not. This phenomenon is nothing but the cause of total internal reflection.
17) Prove that the length of the mirror required to view the complete image of an object is half of the height of the object.
Ans: –
18) What do you mean by refraction of light? How is it different from reflection of light?
Ans: – When the light rays transfer from one medium to the other medium as the refractive index is different the light rays bend when passes from one medium to other, this phenomenon is known as refraction of light.
In case of reflection the rays totally back after it reflected on any strike. But in case of the light is bend after reflection its refraction, so the reflection and refraction are different phenomenon.
19) If the absolute refractive index of glass is 3/2 and that of water is 5/4, then find the ratio of speed of light in water and to that in glass.
Ans: – The ratio of speed of light
= absolute refractive index of glass / refractive index of glass.
= 3/2 / 5/4
=6/5.
20) A fish seems to be at a depth of 75cm from the surface. What is the actual distance from the surface? (Refractive index of water is 1.33).
Ans: – The refractive index = (actual depth / apparent depth)
Here apparent depth = 75 cm; refractive index = 1.33.
So, the actual depth is = (75× 1.33) = 100 cm.