Formative Assesment

Short Answer Based questions for Refraction

1. What is refraction of light?
2. What the speed of light in glass is as compared to speed of light in vacuum. ?
3. What is the unit of refractive index?
4. Why a concave lens is called diverging lens?
5. Define Snell’s law of Refraction.
6. Write the relation between the angle of incidence and angle of refraction for a medium.
7. For total internal reflection to occur, the light must pass from denser to rarer medium. Is this True or false?
8. What type of lens is used in a simple microscope?

Match the column

Column A	Column B
The power of the lens is negative	Convex lens
The lens is diverging	Concave lens
The power of the lens is positive
The lens is converging in nature
The lens is thick at the center but thinner at the edges
The lens is thin in the middle and thicker at the edges
It has real focus
It has virtual focus

Link Comprehension type

Question A lens X has following observation

1. When the objects is placed at infinity, the image is formed at focus of the lens
2. When a object is placed at 60 cm from the lens, A real image is forced at 10 cm from lens on other side
3. The lens has positive Power

Answer following based on the data given above

1. The lens is
   1. Convex
   2. Concave
2. The focal length of the lens is
   1. 20 cm
   2. 10 cm
   3. 25 cm
   4. None of these
3. The power of the lens
   1. 10 D
   2. 5 D
   3. 4 D
   4. None of these
4. When the object is placed at a distance twice the focal length in front of lens, what will be characteristics of the image formed
   1. A real inverted image of same size will be formed at a distance twice the focal length
   2. A real ,erect image of high diminished size will be formed at a distance twice the focal length
   3. A high enlarged image at infinity will be formed
   4. None of these
5. When the lens is placed close to the page of book, the letters of the page appear
   1. Highly diminished
   2. Enlarged
   3. Same size as object
   4. None of these

Fill in the blanks

1. The refractive index of a medium gives an indication of the ……………Ability of that medium
2. When a ray of light goes from water to air, it bends …………From the normal
3. When a ray of light goes from air to glass, it bends ………The normal
4. The speed of light is …… in glass then air
5. The absolute refractive index is always ….. then unity
6. The relative refractive index can be less then ………

Crossword Puzzle

Across
3. The human eye forms the image at this point
5. The medium where speed of light is less
8. A instrument which is used to see details of distant objects
10. The refractive index is equal to reciprocal of the sine of this angle
Down
1. A optical instrument which is used to see small objects
2. It is produced by the dispersion of sunlight by the rain drops in the air
4. The nature of the image formed by the convex lens when the object is placed between optical center and focus
5. The size of the image formed by the concave lens
6. A converging lens
7. It is the defect of eye when it cannot see distant objects clearly
9. The lens having negative power

Long answer type questions

Question 1 What is meant by ‘total internal reflection’? State two essential conditions for total internal reflection to take place. With the help of a ray diagram, illustrate an application of total internal reflection.
Question 2 A concave lens of focal length 15 cm forms an image of 10 cm from the lens.
a) How far is object from the lens?
b) What is the nature of the image?

Question 3 What do you mean by power of the lens? What is the power of a concave lens of focal length 10cm?
Question 4 You are given three medium X, Y, Z .The refractive index of the three medium are n₁ , n₂ and n₃.
It is given that n₁ > n₃ > n₂

1. In which of these does the light travel fastest?
2. In which of these does the light travel lowest?
3. Arrange the medium in ascending order of their optical density?

Question 5 A convex lens forms a real and inverted image of a needle at a distance of 50 cm from it. Where is the needle placed in front of the convex lens if the image is equal to the size of the object? Also, find the power of the lens.
Question 6 A Calculate the focal length of convex lens which produces a virtual image at a distance of 25 cm of an object placed 10cm in front of it.
Question 7 What is lateral shift and optical density?
Question 8 What is scientific name for short sightness and far sightness ? What types of lens are used to correct them?


Solutions

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Class 10 Maths Class 10 Science