Newton's Corpuscular Theory — IISER Physics MCQs with Solutions
Free IISER Physics Newton's Corpuscular Theory MCQs with step-by-step solutions (15 questions). Part of Wave Theory of Light. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Newton's Corpuscular Theory · easy · theory
According to Newton's corpuscular theory, light consists of:
A. Longitudinal mechanical waves in a medium
B. Discrete energy packets called photons
C. Transverse electromagnetic waves
D. Tiny, weightless, perfectly elastic particles (corpuscles) travelling in straight lines ✓ Correct
Solution: Newton proposed that a luminous body emits streams of minute, elastic corpuscles that travel in straight lines at high speed.
Q2 — Newton's Corpuscular Theory · easy · theory
Newton's corpuscular theory could satisfactorily explain:
A. Reflection and rectilinear propagation of light ✓ Correct
B. Interference of light
C. Diffraction of light
D. Polarisation of light
Solution: The corpuscular theory explained rectilinear propagation and reflection (as elastic rebound), but failed for interference, diffraction and polarisation.
Q3 — Newton's Corpuscular Theory · medium · theory
To explain refraction of light into a denser medium, Newton's corpuscular theory required that the speed of light in the denser medium be:
A. Equal to that in the rarer medium
B. Zero
C. Greater than in the rarer medium ✓ Correct
D. Less than in the rarer medium
Solution: Newton assumed corpuscles are attracted towards the denser medium, increasing their velocity — so light should travel faster in a denser medium. This prediction was later proved wrong.
Q4 — Newton's Corpuscular Theory · medium · theory
The prediction of Newton's corpuscular theory that light travels faster in a denser medium was experimentally disproved by:
A. Hertz's experiment
B. Millikan's oil-drop experiment
C. Young's double-slit experiment
D. Foucault's measurement of the speed of light in water ✓ Correct
Solution: Foucault showed that light travels slower in water (denser) than in air, contradicting the corpuscular prediction and supporting the wave theory.
Q5 — Newton's Corpuscular Theory · medium · theory
In Newton's corpuscular theory, the different colours of light were attributed to:
A. Different wavelengths of a wave
B. Corpuscles of different sizes ✓ Correct
C. Different numbers of photons
D. Different frequencies of vibration
Solution: Newton explained colour by proposing that corpuscles of different sizes produce the sensation of different colours.
Q6 — Newton's Corpuscular Theory · medium · theory
Which phenomenon CANNOT be explained by the corpuscular theory of light?
A. Formation of shadows
B. Rectilinear propagation
C. Reflection
D. Interference ✓ Correct
Solution: Interference (and diffraction and polarisation) are wave phenomena that the particle-based corpuscular theory cannot account for.
Q7 — Newton's Corpuscular Theory · medium · theory
A strong point in favour of Newton's corpuscular theory in his time was that it easily explained:
A. The bending of light around small obstacles
B. The coloured fringes in thin films
C. Why light travels in straight lines and casts sharp shadows ✓ Correct
D. The polarisation of reflected light
Solution: Particles travelling in straight lines naturally explain rectilinear propagation and sharp shadows, which is why the theory was widely accepted for a long time.
Q8 — Newton's Corpuscular Theory · medium · theory
One reason Newton rejected the wave theory of light in favour of corpuscles was that:
A. Corpuscles explained interference better than waves
B. Waves could not carry energy
C. Light could not travel through vacuum as a particle
D. Waves were expected to bend around obstacles, yet light appeared to travel in straight lines ✓ Correct
Solution: Newton argued that if light were a wave it should bend appreciably around obstacles (diffraction), whereas light seemed to travel strictly in straight lines — so he preferred corpuscles.
Q9 — Newton's Corpuscular Theory · medium · theory
According to the corpuscular theory, reflection of light occurs because the corpuscles:
A. Are absorbed and re-emitted as waves
B. Interfere destructively at the surface
C. Slow down and reverse due to the medium
D. Undergo perfectly elastic collisions with the surface ✓ Correct
Solution: Reflection was explained as the elastic rebound of corpuscles from a surface, like a perfectly elastic ball bouncing off a wall.
Q10 — Newton's Corpuscular Theory · medium · theory
The corpuscular theory was finally abandoned mainly because it:
A. Required light to have zero speed in vacuum
B. Predicted a higher speed of light in denser media and could not explain interference, diffraction and polarisation ✓ Correct
C. Could not explain the rectilinear propagation of light
D. Could not explain reflection of light
Solution: Its wrong prediction about the speed of light in denser media (disproved by Foucault) together with its failure to explain interference, diffraction and polarisation led to its rejection.
Q11 — Newton's Corpuscular Theory · medium · numerical
For a medium in which sin i / sin r = 1.5, the corpuscular theory predicts the speed of light in the medium (c = 3 × 10⁸ m/s) to be:
A. 3 × 10⁸ m/s
B. 4.5 × 10⁸ m/s ✓ Correct
C. 1.5 × 10⁸ m/s
D. 2 × 10⁸ m/s
Solution: Corpuscular theory (wrongly) predicts v_medium/v_vacuum = sin i/sin r = 1.5, so v = 1.5 × 3 × 10⁸ = 4.5 × 10⁸ m/s — faster than in vacuum, later disproved by Foucault.
Q12 — Newton's Corpuscular Theory · medium · numerical
A ray enters a medium with angle of incidence 53° and refraction 30° (sin53° = 0.8, sin30° = 0.5). The corpuscular prediction for v_medium/v_vacuum is:
A. 1.0
B. 1.6 ✓ Correct
C. 0.8
D. 0.625
Solution: Corpuscular: v_medium/v_vacuum = sin i/sin r = 0.8/0.5 = 1.6 (predicts speeding up — incorrect).
Q13 — Newton's Corpuscular Theory · hard · numerical
For water (n = 4/3), the ratio of the corpuscular-predicted speed to the actual (wave-theory) speed of light in water is:
A. 1 : 1
B. 9 : 16
C. 4 : 3
D. 16 : 9 ✓ Correct
Solution: Corpuscular predicts v_w/v_air = 4/3; the true value is 3/4. Ratio = (4/3)/(3/4) = 16/9.
Q14 — Newton's Corpuscular Theory · medium · numerical
Corpuscular theory predicts, for a glass of n = 1.5, a light speed in glass of (c = 3 × 10⁸ m/s):
A. 4.5 × 10⁸ m/s (wrong) ✓ Correct
B. 1 × 10⁸ m/s
C. 3 × 10⁸ m/s
D. 2 × 10⁸ m/s (correct)
Solution: It sets v = nc = 1.5 × 3 × 10⁸ = 4.5 × 10⁸ m/s. Wave theory correctly gives v = c/n = 2 × 10⁸ m/s.
Q15 — Newton's Corpuscular Theory · hard · numerical
If the angle of incidence is 60° and the corpuscular-predicted speed ratio v₂/v₁ is √3, the angle of refraction is (sin60° = √3/2):
A. 30° ✓ Correct
B. 60°
C. 45°
D. 20°
Solution: sin i/sin r = v₂/v₁ = √3 ⇒ sin r = sin60°/√3 = (√3/2)/√3 = 1/2 ⇒ r = 30°.