Physical World and Measurement Quiz - ICSE Class 11 Physics
Free practice quiz: Physical World and Measurement (ICSE Class 11 Physics). 47 multiple-choice questions with answers and explanations. Play online, no sign-up needed.
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A fundamental constant in physics, Planck's constant (h), relates the energy of a photon to its frequency. If the energy of a photon is given by E = hν, and the momentum of a photon is given by p = h/λ, where λ is the wavelength. What is the dimensionality of Planck's constant?
- [ML^2T^-1]
- [MLT^-2]
- [M^0L^2T^-2]
- [ML^1T^-1]
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Answer: A. [ML^2T^-1]
We know that Energy (E) has dimensions of [ML^2T^-2] and Frequency (ν) has dimensions of [T^-1]. From E = hν, h = E/ν. Therefore, the dimensions of h are [ML^2T^-2] / [T^-1] = [ML^2T^-1]. Alternatively, Momentum (p) has dimensions of [MLT^-1] and wavelength (λ) has dimensions of [L]. From p = h/λ, h = pλ. Therefore, the dimensions of h are [MLT^-1] * [L] = [ML^2T^-1]. Both methods yield the same dimensions.
The SI unit of luminous intensity is:
- Watt
- Joule
- Candela
- Newton
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Answer: C. Candela
Candela (cd) is the SI base unit of luminous intensity, measuring the power emitted by a light source in a particular direction. Watt is the SI unit of power, Joule is the SI unit of energy, and Newton is the SI unit of force.
Which physical quantity has the same dimensions as that of energy?
- Momentum
- Power
- Torque
- Pressure
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Answer: C. Torque
Energy has dimensions [ML^2T^-2]. Momentum has dimensions [MLT^-1]. Power has dimensions [ML^2T^-3]. Torque is calculated as force times perpendicular distance (Force × distance), so its dimensions are [MLT^-2] × [L] = [ML^2T^-2]. Pressure has dimensions [ML^-1T^-2]. Therefore, Torque has the same dimensions as energy.
A student uses a meter scale to measure the length of a table and records it as 1.25 m. The least count of the meter scale is 1 mm. What is the percentage error in this measurement?
- 0.8%
- 0.08%
- 1.25%
- 0.125%
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Answer: B. 0.08%
The least count is 1 mm = 0.001 m. The measured value is 1.25 m. The percentage error is (Least Count / Measured Value) × 100%. Percentage Error = (0.001 m / 1.25 m) × 100% = (1/1250) × 100% = 100/1250 % = 1/12.5 % = 0.08%.
The order of magnitude of the diameter of a hydrogen atom is approximately:
- 10⁻¹⁰ m
- 10⁻⁸ m
- 10⁻¹⁵ m
- 10⁻²⁷ m
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Answer: A. 10⁻¹⁰ m
The diameter of a hydrogen atom is on the order of 1 Angstrom (Å), which is equal to 10⁻¹⁰ meters. 10⁻⁸ m would be the size of a cell. 10⁻¹⁵ m is the order of magnitude of the nucleus of an atom. 10⁻²⁷ m is roughly the mass of a proton in kg, not a length scale.