A lactometer operates on the principle of: MCQ with Answer and Explanation

A lactometer operates on the principle of:
A. Newton's Law of Viscosity
B. Pascal's Law
C. Archimedes' Principle
D. Bernoulli's Theorem
Answer: Option C
Solution (By JKSSB Mock Tests)
A lactometer is a specific type of hydrometer used to test the purity of milk by measuring its relative density. All hydrometers, including lactometers, work on Archimedes' Principle of buoyancy. They float at a depth that depends directly on the density of the liquid; they sink deeper in less dense liquids (like milk heavily diluted with water).

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Practice More Physics Questions

Question #1
Archimedes' principle is used in
A. Barometer
B. Hydrometer
C. Thermometer
D. Seismograph

Correct Answer: Option B


Explanation:
Hydrometer floats based on density, uses buoyancy principle.

This question belongs to: Science Physics
Question #2
Nuclear fusion requires
A. High temperature only
B. Low temperature and high pressure
C. High temperature and high pressure
D. Low temperature and low pressure

Correct Answer: Option C


Explanation:
Overcome Coulomb repulsion between nuclei, need extreme temperature and pressure.

This question belongs to: Science Physics
Question #3
When white light passes through a prism, it disperses into colors because:
A. Prism absorbs some colors
B. Different colors have different speeds in glass
C. Total internal reflection occurs
D. Different colors have different frequencies

Correct Answer: Option B


Explanation:
Dispersion occurs because refractive index of glass varies with wavelength (color): n ∝ 1/λ approximately. Since v = c/n, different colors travel at different speeds in glass, causing different refraction angles (Snell's law). Frequency remains constant across media; wavelength changes. Option B is true but not the direct cause; speed difference causes angle difference. Memory tip: 'VIBGYOR: Violet bends most (slowest in glass), red least'. This conceptual question tests understanding of dispersion mechanism, crucial for optics in competitive exams. Always distinguish cause (speed variation) from property (frequency/wavelength).

This question belongs to: Science Physics