Every Book Back multiple-choice question from Optics (10th Standard Science, Samacheer Kalvi) — each with the correct option highlighted and a clear, worked explanation. Free to read in English and Tamil.
Q1
The refractive index of four substances A, B, C and D are 1.31, 1.43, 1.33, 2.4 respectively. The speed of light is maximum in
- A. Substance ACorrect
- B. Substance B
- C. Substance C
- D. Substance D
Explanation. The speed of light in a medium is inversely proportional to its refractive index. Since substance A has the lowest refractive index of 1.31, the speed of light will be maximum in it.
Q2
Where should an object be placed so that a real and inverted image of same size is obtained by a convex lens?
- A. at f
- B. at 2fCorrect
- C. infinity
- D. between f and 2f
Explanation. When an object is placed at the centre of curvature (2f) of a convex lens, a real and inverted image of the same size is formed at 2f on the other side of the lens.
Q3
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 lightCorrect
- D. a coloured beam of light
Explanation. Light rays originating from the principal focus of a convex lens become parallel to the principal axis after refraction, thereby producing a parallel beam of light.
Q4
Magnification of a convex lens is
- A. positive
- B. negative
- C. either positive or negativeCorrect
- D. zero
Explanation. A convex lens can produce both real and virtual images. Since virtual images are erect (positive magnification) and real images are inverted (negative magnification), the magnification can be either positive or negative.
Q5
A convex lens forms a real, diminished point sized image at focus. Then the position of the object is at
- A. focus
- B. infinityCorrect
- C. at 2f
- D. between f and 2f
Explanation. When an object is placed at infinity, the parallel light rays incident on a convex lens converge at the principal focus, forming a real, inverted, and point-sized image.
Q6
Power of a lens is -4D, then its focal length is
- A. 4 m
- B. -40 m
- C. -0.25 mCorrect
- D. -2.5 m
Explanation. The power P of a lens is the reciprocal of its focal length in metres (f = 1/P). Here, f = 1/(-4 D) = -0.25 m.
Q7
In a myopic eye, the image of the object is formed
- A. behind the retina
- B. on the retina
- C. in front of the retinaCorrect
- D. on the blind spot
Explanation. Myopia occurs due to increased converging power of the eye lens or lengthening of the eyeball, causing parallel rays from distant objects to focus in front of the retina.
Q8
The eye defect 'presbyopia' can be corrected by
- A. convex lens
- B. concave lens
- C. convex mirror
- D. bifocal lensesCorrect
Explanation. Presbyopia is caused by ageing where the eye loses its power of accommodation. It is corrected using bifocal lenses, containing both concave and convex components.
Q9
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 cmCorrect
- 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
Explanation. A convex lens of short focal length is preferred for magnifying small letters. A shorter focal length of 5 cm provides higher magnifying power than a 10 cm focal length.
Q10
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 < VRCorrect
- D. VB < VG > VR
Explanation. In a glass prism, the refractive index decreases as wavelength increases. Red has the longest wavelength (lowest index, highest speed) and blue has the shortest (highest index, lowest speed). Thus, VB < VG < VR.
About these Optics questions
These are the Book Back multiple-choice questions for Optics from the Tamil Nadu State Board (Samacheer Kalvi) 10th Standard Science syllabus. Each question shows the correct option and an original, step-by-step explanation so you understand the method, not just the answer. Use the answer key above to jump to any question, then take the practice test to check yourself under exam-like conditions.
Frequently asked questions
How many MCQs are there in Optics?
This chapter has 10 book-back multiple-choice questions, each with the correct answer and a step-by-step explanation.
Are these 10th Standard Science MCQs free to practise online?
Yes. Every question, answer and explanation here is free, and you can also take them as a timed practice test.
Where can I find the Optics book-back answers?
The correct option for each question is highlighted on this page with a worked explanation, plus a quick answer-key summary at the top.
