Chapter Exam

Chapter 2: Optics — Online MCQ Test

Q: What is the SI unit of power of a lens?

Answer: B. Dioptre — The SI unit of power of a lens is dioptre (D), which is equal to 1 m⁻¹.

Q: According to Rayleigh's scattering law, the amount of scattering (S) is inversely proportional to which power of the wavelength (λ) of light?

Answer: D. Fourth power — Rayleigh's scattering law states that $S \propto 1/\lambda^4$, meaning scattering is inversely proportional to the fourth power of wavelength.

Q: A convex lens forms a real and inverted image of the exact same size as the object. Where should the object be placed in front of the lens?

Answer: C. At 2F — When an object is placed at 2F of a convex lens, a real, inverted image of the same size is formed at 2F on the other side.

Q: In Raman scattering, what are the spectral lines called that have frequencies lower than that of the incident light?

Answer: B. Stokes lines — Stokes lines have lower frequency (longer wavelength) than the incident light, while Anti-Stokes lines have higher frequency.

Q: Two thin lenses of focal lengths +10 cm and -20 cm are placed in contact. If an object is placed 30 cm in front of this lens combination, at what distance from the combination is the image formed?

Answer: B. +60 cm — Combined focal length: $1/F = 1/10 - 1/20 = 1/20 \implies F = +20\text{ cm}$. Using $1/v - 1/u = 1/F$ with $u = -30\text{ cm}$: $1/v = 1/20 - 1/30 = 1/60 \implies v = +60\text{ cm}$.

SCIENCE · CLASS 10th · Tamil Nadu State Board

Practice Chapter 2: Optics with a free chapter-wise online MCQ test for Tamil Nadu State Board CLASS 10th SCIENCE. This chapter covers: Focusing on light behavior this chapter explores refraction reflection lenses and dispersion. Students examine the human eye vision defects microscope telescope working principles.... AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter 2: Optics — Important Questions & Answers (FAQ)

Frequently asked questions from Tamil Nadu State Board CLASS 10th SCIENCE — Chapter 2: Optics, with answers and explanations. These are sample questions; the exam has its own separate question set.

What is the SI unit of power of a lens?

A. Meter
B. Dioptre ✓
C. Watt
D. Joule

Answer: B. Dioptre
The SI unit of power of a lens is dioptre (D), which is equal to 1 m⁻¹.

According to Rayleigh's scattering law, the amount of scattering (S) is inversely proportional to which power of the wavelength (λ) of light?

A. First power
B. Second power
C. Third power
D. Fourth power ✓

Answer: D. Fourth power
Rayleigh's scattering law states that $S \propto 1/\lambda^4$, meaning scattering is inversely proportional to the fourth power of wavelength.

A convex lens forms a real and inverted image of the exact same size as the object. Where should the object be placed in front of the lens?

A. At principal focus F
B. Between F and 2F
C. At 2F ✓
D. Beyond 2F

Answer: C. At 2F
When an object is placed at 2F of a convex lens, a real, inverted image of the same size is formed at 2F on the other side.

In Raman scattering, what are the spectral lines called that have frequencies lower than that of the incident light?

A. Rayleigh lines
B. Stokes lines ✓
C. Anti-Stokes lines
D. Fraunhofer lines

Answer: B. Stokes lines
Stokes lines have lower frequency (longer wavelength) than the incident light, while Anti-Stokes lines have higher frequency.

Two thin lenses of focal lengths +10 cm and -20 cm are placed in contact. If an object is placed 30 cm in front of this lens combination, at what distance from the combination is the image formed?

A. +30 cm
B. +60 cm ✓
C. -30 cm
D. +15 cm

Answer: B. +60 cm
Combined focal length: $1/F = 1/10 - 1/20 = 1/20 \implies F = +20\text{ cm}$. Using $1/v - 1/u = 1/F$ with $u = -30\text{ cm}$: $1/v = 1/20 - 1/30 = 1/60 \implies v = +60\text{ cm}$.