Refraction and dispersion through a prism — practice questions

Question 1 · difficulty L1 · recall

A prism deviates a light ray because of

• A. refraction at its two nonparallel faces
• B. reflection only at a single plane face
• C. diffraction from its edges only
• D. absorption without changing direction

Question 2 · difficulty L1 · understanding

At minimum deviation through a prism, the path is symmetric so that

• A. incidence angle is zero
• B. angle of incidence equals angle of emergence
• C. emergence is 90°
• D. refraction occurs only at one face

Question 3 · difficulty L2 · understanding

For a prism of angle A at minimum deviation δm, the refractive index is given by

• A. n=sin(A/2)/sin[(A+δm)/2]
• B. n=(A+δm)/A for all angles
• C. n=sin[(A+δm)/2]/sin(A/2)
• D. n=tanδm/tanA

Question 4 · difficulty L2 · application

Dispersion is the splitting of white light because refractive index

• A. is identical for all wavelengths
• B. depends only on prism mass
• C. becomes zero for violet
• D. depends on wavelength

Question 5 · difficulty L3 · application

In ordinary glass, which visible colour is generally deviated most by a prism?

• A. Violet
• B. Red
• C. Yellow
• D. All equally

Question 6 · difficulty L3 · application

In ordinary glass, which visible colour is deviated least by a prism?

• A. Violet
• B. Red
• C. Blue
• D. All equally

Question 7 · difficulty L4 · analysis

A prism produces minimum deviation when a ray passes so that the internal refraction angles are each

• A. A
• B. δm/2
• C. A/2
• D. 90°

Question 8 · difficulty L4 · analysis

White light enters a prism and emerges as a spectrum. Which ordering from least to greatest deviation is expected?

• A. Violet to red
• B. Green to red to violet only with violet least
• C. All colours overlap exactly
• D. Red to violet

Question 9 · difficulty L5 · analysis

If a prism is immersed in a liquid whose refractive index approaches that of the prism material, its angular deviation generally

• A. decreases
• B. increases without bound
• C. stays exactly the same
• D. reverses for every wavelength

Question 10 · difficulty L5 · analysis

A monochromatic ray passes through a prism at minimum deviation. If the prism is rotated slightly away from this condition while wavelength stays fixed, the deviation

• A. decreases further
• B. increases
• C. remains exactly at the minimum
• D. must become zero