## 10th Science Book Back Answers  Unit 2 – Optics:

Samacheer Kalvi 10th Standard Science Book Back Questions with Answers PDF uploaded and the same given below. Class-tenth candidates and those preparing for TNPSC exams can check the New Science Book Back Question and Answers PDF below.  Samacheer Kalvi Class 10th Std Science Book Back Answers Physics Unit 2 – Optics Solutions are available below. Complete solutions for all 23 Units’ book back questions with a solutions guide uploaded and available on our site. Check the complete Samacheer Kalvi 10th Science Unit 2 Answers below:

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### Samacheer Kalvi 10th Science Book Back Answers Physics Unit 2 – Optics

Samacheer Kalvi 10th Science Book Subject One Mark, Two Mark Guide questions and answers are below. Check Science Book Back Questions with Answers. Take the printout and use it for exam purposes.

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#### Unit 2: Optics

1. The refractive index of four substances A, B, C, and D are 1.31, 1.43, 1.33, and 2.4 respectively. The speed of light is maximum in
a. A     b. B     c. C     d. D
Ans : (a) A

2. Where should an object be placed so that a real and inverted image of the same size is obtained by a convex lens
a. f       b. 2f       c. infinity      d. between f and 2f
Ans : (b) 2f

3. A small bulb is placed at the principal focus of a convex lens. When the bulb is switched on, the lens will produce
a. a convergent beam of light    b. a divergent beam of light
c. a parallel beam of light           d. a coloured beam of light
Ans : (c) a parallel beam of light

4. Magnification of a convex lens is
a. positive                                     b. negative
c. either positive or negative   d. zero
Ans : (c) either positive or negative

5. A convex lens forms a real, diminished point-sized image at focus. Then the position of the object is at
a. focus    b. infinity    c. at 2f    d. between f and 2f
Ans : (b) infinity

6. Power of a lens is –4D, then its focal length is
a. 4m b. –40 m c. –0.25 m d. –2.5 m
Ans: (c) –0.25 m

7. In a myopic eye, the image of the object is formed
a. behind the retina    b. on the retina    c. in front of the retina    d. on the blind spot
Ans : (c) in front of the retina

8. The eye defect ‘presbyopia’ can be corrected by
a. convex lens b. concave lens c. convex mirror d. bifocal lenses
Ans : (d) bifocal lenses

9. Which of the following lens would you prefer to use while reading small letters found in a dictionary?
a. A convex lens of focal length 5 cm b. A concave lens of focal length 5 cm
c. A convex lens of focal length 10 cm d. A concave lens of focal length 10 cm
Ans : (a) A convex lens of focal length 5 cm

10. If VB, VG, VR be the velocity of blue, green and red light respectively in a glass prism, then which of the following statement gives the correct relation?
a. VB = VG = VR    b. VB > VG > VR    c. VB < VG < VR    d. VB < VG > VR
Ans : (b) VB > VG > VR

II. Fill in the blanks:
1. The path of the light is called as. Ans: ray
2. The refractive index of a transparent medium is always greater than   Ans: one
3. If the energy of incident beam and the scattered beam are the same, then the scattering of light is called as scattering. Ans: Elastic
4. According to Rayleigh’s scattering law, the amount of scattering of light is inversely proportional to the fourth
power of its. Ans: wavelength
5. Amount of light entering into the eye is controlled by. Ans: iris

III. True or False (Correct the Statement if it is false)
1. Velocity of light is greater in a denser medium than in rarer medium.
Ans: False. The velocity of light is greater in the rare medium than in denser medium.

2. The power of the lens depends on the focal length of the lens. Ans: True.

3. Increase in the converging power of the eye lens causes ‘hypermetropia’. Ans: True.

4. The convex lens always gives a small virtual image.
Ans: False. Only concave lens always gives a small virtual image.

IV. Match the following:

 1 Retina (a) Pathway of light 2 Pupil (b) Far point comes closer 3 Ciliary muscles (c) Near point moves away 4 Myopia (d) Screen of the eye 5 Hypermetropia (e) Power of accommodation

Ans:

 Column I Column II 1 Retina d. Screen of the eye 2 Pupil b. Path way of light 3 Ciliary muscles f. Power of accomodation 4 Myopia b. Far point comes closer 5 Hypermetropia c. Near point moves away

V. Assertion and Reason
Mark the correct choice as
a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion.
b) If both the assertion and the reason are true, but the reason is not the correct explanation of the assertion.
c) Assertion is true, but the reason is false.
d) Assertion is false, but the reason is true.

1. Assertion: If the refractive index of the medium is high (denser medium) the velocity of the light in that
medium will be small.
Reason: Refractive index of the medium is inversely proportional to the velocity of the light.
Ans : (a) both the assertion and the reason are true and the reason is the correct explanation of the assertion.

2. Assertion: Myopia is due to the increase in the converging power of the eye lens.
Reason: Myopia can be corrected with the help of a concave lens.
Ans : (b) both the assertion and the reason are true, but the reason is not the correct explanation of the assertion.