EST2 HIGH SCHOOL PHYSICS
๐ฆ OPTICS – LIGHT, REFLECTION, REFRACTION, DIFFRACTION
๐ฅ 30 HARD QUESTIONS
No pictures – just pure physics!
Directions: Choose the best answer for each question (A – E). Answers are provided below each question.
Questions 1 – 10
1. The speed of light in a vacuum is approximately:
A) 3.0 × 10⁶ m/s
B) 3.0 × 10⁸ m/s
C) 3.0 × 10¹⁰ m/s
D) 3.0 × 10⁵ m/s
E) 3.0 × 10⁷ m/s
Answer: B
2. What is the angle of reflection if a light ray strikes a flat mirror at an angle of 30° to the normal?
A) 60°
B) 30°
C) 90°
D) 150°
E) 0°
Answer: B
3. A ray of light passes from air into glass. What happens to its speed?
A) It increases
B) It stays the same
C) It decreases
D) It doubles
E) It becomes zero
Answer: C
4. Snell's Law relates which two quantities?
A) Speed and frequency
B) Angle of incidence and angle of reflection
C) Angle of incidence and angle of refraction
D) Wavelength and amplitude
E) Intensity and brightness
Answer: C
5. Total internal reflection occurs when light travels from:
A) A denser medium to a rarer medium at an angle less than the critical angle
B) A rarer medium to a denser medium
C) A denser medium to a rarer medium at an angle greater than the critical angle
D) Vacuum to glass
E) Any medium at 90° incidence
Answer: C
6. The phenomenon where light bends around obstacles is called:
A) Reflection
B) Refraction
C) Diffraction
D) Dispersion
E) Polarization
Answer: C
7. What is the critical angle for light going from glass (n = 1.5) to air (n = 1)?
A) 41.8°
B) 48.6°
C) 90°
D) 30°
E) 60°
Answer: A
8. Which color of visible light has the longest wavelength?
A) Violet
B) Blue
C) Green
D) Yellow
E) Red
Answer: E
9. A concave mirror has a focal length of 10 cm. An object is placed 30 cm from the mirror. What is the image distance?
A) 15 cm
B) 10 cm
C) 7.5 cm
D) 30 cm
E) 60 cm
Answer: A
10. The dispersion of white light into its colors is caused by:
A) Diffraction
B) Interference
C) Refraction with different wavelengths bending by different amounts
D) Reflection
E) Polarization
Answer: C
Questions 11 – 20
11. A convex lens has a focal length of 20 cm. What is the power of the lens in diopters?
A) 0.05 D
B) 0.2 D
C) 5 D
D) 20 D
E) 50 D
Answer: C
12. Diffraction is most noticeable when the obstacle size is:
A) Much larger than the wavelength
B) Equal to the wavelength
C) Much smaller than the wavelength
D) Zero
E) Infinite
Answer: B
13. What is the index of refraction of a medium if the speed of light in it is 2.0 × 10⁸ m/s?
A) 1.0
B) 1.33
C) 1.5
D) 2.0
E) 0.67
Answer: C
14. A double-slit interference pattern is produced. If the slit separation is increased, the fringe spacing will:
A) Increase
B) Decrease
C) Stay the same
D) Become zero
E) Become infinite
Answer: B
15. A ray of light is incident on a plane mirror at 45°. What is the angle between the incident ray and the reflected ray?
A) 45°
B) 90°
C) 135°
D) 180°
E) 0°
Answer: B
16. Which phenomenon proves that light is a wave?
A) Reflection
B) Refraction
C) Interference
D) Shadow formation
E) Rectilinear propagation
Answer: C
17. The focal length of a convex mirror is:
A) Always positive
B) Always negative
C) Zero
D) Equal to the radius of curvature
E) Infinite
Answer: B
18. The wavelength of light in a medium with index of refraction n is:
A) ฮป₀ × n
B) ฮป₀ / n
C) ฮป₀ + n
D) ฮป₀ - n
E) ฮป₀ × n²
Answer: B
19. For a concave mirror, a real image is formed when the object is placed:
A) At the focus
B) Between the focus and the mirror
C) Beyond the center of curvature
D) At the center of curvature
E) None of the above
Answer: C
20. The bending of light as it passes from one medium to another is due to a change in:
A) Frequency
B) Wavelength
C) Speed
D) Amplitude
E) Intensity
Answer: C
Questions 21 – 30
21. What is the minimum distance between an object and its real image formed by a concave mirror?
A) f
B) 2f
C) 4f
D) Zero
E) Infinite
Answer: C
22. A ray of light enters a glass slab and exits parallel to its original path. This is because:
A) Total internal reflection occurs
B) The slab has zero refractive index
C) The two refractions cancel each other's deviation
D) Light speeds up inside the slab
E) The slab is perfectly transparent
Answer: C
23. The resolving power of a microscope is limited by:
A) Reflection
B) Refraction
C) Diffraction
D) Dispersion
E) Polarization
Answer: C
24. In Young's double-slit experiment, what happens to the fringe width if the slit distance is doubled?
A) Doubles
B) Halves
C) Quadruples
D) Remains the same
E) Becomes zero
Answer: B
25. The critical angle for a water-air interface is approximately (n = 1.33):
A) 42°
B) 49°
C) 53°
D) 61°
E) 90°
Answer: B
26. A diffraction grating has 500 lines per mm. The grating spacing (d) is:
A) 5 × 10⁻⁶ m
B) 2 × 10⁻⁶ m
C) 5 × 10⁻³ m
D) 2 × 10⁻³ m
E) 5 × 10⁻⁴ m
Answer: B
27. For constructive interference in a double-slit experiment, the path difference must be:
A) mฮป/2
B) mฮป
C) (2m+1)ฮป/2
D) (2m+1)ฮป
E) mฮป/4
Answer: B
28. A convex lens forms a virtual image when the object is placed:
A) At 2F
B) Between F and the lens
C) At infinity
D) At F
E) Beyond 2F
Answer: B
29. In a plane mirror, the image is:
A) Real and inverted
B) Virtual and upright
C) Real and upright
D) Virtual and inverted
E) Magnified and real
Answer: B
30. The ability of a lens to converge or diverge light is measured by its:
A) Focal length
B) Power
C) Radius of curvature
D) Aperture
E) Magnification
Answer: B
✅ Good luck on your EST2 Physics Exam! Optics mastery starts here!
Posted for practice purposes only.
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