Ray Optics

Class 12 | Physics

Concepts

• Refraction at Convex surface
• Refraction in Glass Slab
• Refraction of light through a prism
• Magnification in Cassegrain Telescope
• Important formulae in ray optics

Concept Videos

1. Reflection on curved surfaces or mirrors
2. Concave mirror problem
3. Concave mirror problem 2
4. Concave mirror problem 3
5. Car rear view mirror problem 4
6. Astronomical telescope with image at least distance of distinct vision
7. Refraction at convex surface drawing practice
8. Refraction in glass slab
9. Ray optics formulae set 1
10. Ray optics formulae set 2
11. Ray optics formulae set 3
12. Problem based on resolving power of telescope
13. Resolving power of optical instruments
14. Resolving power of a telescope and Brewster’s law

Refraction at Convex Surface

Refraction in Glass Slab

Important Formulae

QUIZ

MCQ Assignment Set-1

1. When light enters a glass slab from air, it:
   a) Speeds up
   b) Slows down
   c) Remains unchanged
   d) Changes direction randomly
2. In which direction does the normal line to the glass-air interface point when light enters the glass?
   a) Away from the glass
   b) Towards the glass
   c) Parallel to the glass surface
   d) None of the above
3. The angle of incidence is 30 degrees. What is the angle of refraction when light passes from air into a glass slab (μ = 1.5)?
   a) 20 degrees
   b) 30 degrees
   c) 40 degrees
   d) 50 degrees
4. What happens to the wavelength of light as it enters a glass slab from air?
   a) It decreases
   b) It increases
   c) It remains the same
   d) It depends on the color of light
5. If a light ray is incident normally on a glass slab, what is the angle of refraction inside the slab?
   a) 0 degrees
   b) 30 degrees
   c) 45 degrees
   d) 90 degrees
6. When light exits the glass slab and enters the air again, it:
   a) Bends away from the normal
   b) Bends towards the normal
   c) Continues in a straight line
   d) Depends on the angle of incidence
7. What is the minimum angle of incidence for total internal reflection to occur at the air-glass interface?
   a) 0 degrees
   b) 30 degrees
   c) 45 degrees
   d) 90 degrees
8. When does total internal reflection occur?
   a) When the angle of incidence is greater than the critical angle
   b) When the angle of incidence is less than the critical angle
   c) When the angle of incidence is equal to the critical angle
   d) It never occurs in glass
9. The critical angle for total internal reflection depends on:
   a) The speed of light in the glass
   b) The wavelength of light
   c) The angle of incidence
   d) The color of light
10. Which of the following colors of light is bent the most when passing through a glass slab?
    a) Red
    b) Blue
    c) Green
    d) All colors bend the same amount
11. What is the refractive index of a glass slab if the speed of light in the glass is 2 × 10^8 m/s and in air is 3 × 10^8 m/s?
    a) 1.5
    b) 2
    c) 0.5
    d) 3
12. When light enters a glass slab, what happens to its frequency?
    a) It increases
    b) It decreases
    c) It remains the same
    d) It depends on the angle of incidence
13. Which of the following statements about refraction in a glass slab is true?
    a) The incident ray, refracted ray, and normal all lie in the same plane.
    b) The refracted ray is always parallel to the incident ray.
    c) The refracted ray always bends away from the normal.
    d) The refracted ray is always perpendicular to the incident ray.
14. When does the lateral displacement of a light ray passing through a glass slab become zero?
    a) At the point of entry into the glass
    b) At the point of exit from the glass
    c) At a certain angle of incidence
    d) Lateral displacement is always zero.
15. If the angle of incidence is 45 degrees, what is the angle of refraction when light enters a glass slab (μ = 1.5)?
    a) 15 degrees
    b) 30 degrees
    c) 45 degrees
    d) 60 degrees
16. What happens to the speed of light when it enters a glass slab from air?
    a) It increases
    b) It decreases
    c) It remains the same
    d) It depends on the color of light
17. The refractive index of a medium is a measure of its:
    a) Density
    b) Transparency
    c) Reflectivity
    d) Conductivity
18. When light passes from a medium with a higher refractive index to a medium with a lower refractive index, it:
    a) Bends towards the normal
    b) Bends away from the normal
    c) Does not bend
    d) Reflects completely
19. What is the angle of incidence for which the angle of refraction is 90 degrees when light enters a glass slab?
    a) 0 degrees
    b) 30 degrees
    c) 45 degrees
    d) 90 degrees
20. In a glass slab, which of the following properties does not change for light passing through it?
    a) Speed
    b) Wavelength
    c) Frequency
    d) Angle of refraction

Refraction of light through a prism

Key-1

1. b) Slows down
2. b) Towards the glass
3. c) 40 degrees
4. c) It remains the same
5. a) 0 degrees
6. b) Bends towards the normal
7. a) 0 degrees
8. a) When the angle of incidence is greater than the critical angle
9. c) the incident angle
10. c) Green
11. a) 1.5
12. c) It remains the same
13. a) The incident ray, refracted ray, and normal all lie in the same plane.
14. d) Lateral displacement is always zero.
15. a) 15 degrees
16. b) It decreases
17. a) Density
18. a) Bends towards the normal
19. c) 45 degrees
20. c) Frequency

Magnification in Cassegrain Telescope

Important Formulae in Ray Optics

Questions Bank

1. Ray optics one mark questions | Key
2. Ray optics 3 marks question | Key

MCQ in Resolving power of optical instruments

1. The resolving power of an optical instrument is its ability to:
   a) Magnify objects
   b) Separate two closely spaced objects
   c) Produce a sharp image
   d) Increase the brightness of an image
2. Which of the following factors does NOT affect the resolving power of an optical instrument?
   a) Wavelength of light used
   b) Aperture size
   c) Focal length of the lens
   d) Size of the object
3. Resolving power is usually defined in terms of the minimum angle between two objects that can be distinguished. What is this angle called?
   a) Angular separation
   b) Angular diameter
   c) Angular resolution
   d) Angular dispersion
4. In which type of microscope is the resolving power limited by the wavelength of light used?
   a) Electron microscope
   b) Compound microscope
   c) Scanning tunneling microscope
   d) Optical microscope
5. The resolving power of an optical instrument is directly proportional to:
   a) Wavelength of light used
   b) Square of the aperture size
   c) Focal length of the lens
   d) Size of the object
6. In a telescope, what is the primary purpose of the objective lens or mirror?
   a) To magnify the image
   b) To collect light from distant objects
   c) To focus the image on the eyepiece
   d) To reduce aberrations
7. Which of the following factors can improve the resolving power of an optical instrument?
   a) Decreasing the wavelength of light
   b) Increasing the size of the object
   c) Decreasing the focal length of the lens
   d) Increasing the distance between the lens and the object
8. Which type of aberration is caused by the inability of a lens to bring all colors of light to a common focus?
   a) Spherical aberration
   b) Chromatic aberration
   c) Coma
   d) Astigmatism
9. Which of the following optical instruments is primarily used for viewing objects at a nanometer scale?
   a) Optical microscope
   b) Electron microscope
   c) Telescope
   d) Microscope
10. The resolving power of an optical instrument is measured in units of:
    a) Watts
    b) Amperes
    c) Meters
    d) Arcseconds
11. The resolving power of an optical instrument can be improved by:
    a) Decreasing the wavelength of light
    b) Increasing the aperture size
    c) Increasing the object size
    d) Increasing the magnification
12. Which type of telescope uses a concave mirror as the primary optical element?
    a) Refracting telescope
    b) Reflecting telescope
    c) Compound telescope
    d) Galilean telescope
13. Which of the following is NOT a common method for reducing chromatic aberration in optical instruments?
    a) Using a lens made of a single type of glass
    b) Using multiple lenses with different dispersions
    c) Using a diffractive optical element
    d) Using achromatic lenses
14. The resolving power of an optical instrument is best defined as its ability to:
    a) Produce a bright image
    b) Magnify an object
    c) Separate two nearby objects
    d) Eliminate spherical aberration
15. The resolving power of a microscope can be improved by:
    a) Decreasing the diameter of the objective lens
    b) Increasing the distance between the objective and eyepiece
    c) Increasing the numerical aperture
    d) Decreasing the wavelength of light used
16. In an optical instrument, the term “numerical aperture” is associated with:
    a) Brightness of the image
    b) Magnification power
    c) Resolving power
    d) Chromatic aberration
17. Which type of microscope is commonly used for observing living biological specimens?
    a) Scanning electron microscope (SEM)
    b) Transmission electron microscope (TEM)
    c) Confocal microscope
    d) Optical microscope
18. The resolving power of an optical instrument is limited by the:
    a) Magnification
    b) Focal length
    c) Wavelength of light used
    d) Aperture size
19. Which type of aberration causes point sources of light to appear as small streaks or lines in the image?
    a) Spherical aberration
    b) Coma
    c) Astigmatism
    d) Chromatic aberration
20. The resolving power of an optical instrument is typically measured in units of:
    a) Pixels
    b) Arcminutes
    c) Nanometers
    d) Rayleighs

Key For Resolving power of optical instruments

Key

1. b) Separate two closely spaced objects
2. c) Focal length of the lens
3. c) Angular resolution
4. d) Optical microscope
5. b) Square of the aperture size
6. b) To collect light from distant objects
7. b) Increasing the size of the object
8. b) Chromatic aberration
9. b) Electron microscope
10. d) Arcseconds
11. a) Decreasing the wavelength of light
12. b) Reflecting telescope
13. a) Using a lens made of a single type of glass
14. c) Separate two nearby objects
15. c) Increasing the numerical aperture
16. c) Resolving power
17. d) Optical microscope
18. c) Wavelength of light used
19. b) Coma
20. d) Rayleighs