Grade 12 Advanced Physics Notes - Term 1 (2025-2026)

Overview

The notes provided correspond to a Grade 12 Advanced Physics curriculum for the term 1 of the 2025-2026 academic year. The focus is on multiple-choice questions (MCQ), practice problems, and detailed scientific concepts related to light, optics, and their applications.

Multiple Choice Questions (MCQ)

  • Page 7

    • Practice Problem Examples:

    1. What is the SI unit of luminous flux?

      • a) Candela

      • b) Lux

      • c) Lumen

      • d) Watt

    2. The illuminance on a surface is measured in:

      • a) Lumens

      • b) Candelas

      • c) Lux

      • d) Joules

    3. Which quantity describes the total light power emitted by a source?

      • a) Luminous Intensity

      • b) Illuminance

      • c) Luminous Flux

      • d) Wavelength

    • Answers:

    1. c) Lumen

    2. c) Lux

    3. c) Luminous Flux

  • Page 10

    • Practice Problem Examples:

    1. Diffraction is best described as:

      • a) The change in wave speed in a new medium.

      • b) The bending of a wave as it passes the edge of a barrier.

      • c) The superposition of two waves meeting.

      • d) The change in frequency due to motion.

    2. Which phenomenon occurs when a water wave spreads out after passing through a narrow opening in a barrier?

      • a) Refraction

      • b) Reflection

      • c) Diffraction

      • d) Dispersion

    3. The bending of light around the edge of an obstacle is an example of:

      • a) Reflection

      • b) Refraction

      • c) Diffraction

      • d) Polarization

    • Answers:

    1. b) The bending of a wave as it passes the edge of a barrier.

    2. c) Diffraction

    3. c) Diffraction

Polarization of Light

  • Definition:

    • Polarization is the production of light with a specific pattern of oscillation.

    • When the electric field of a light wave oscillates in random directions, the light is referred to as nonpolarized.

  • Polarization Process:

    • A polarizer has a polarizing axis. Light with an electric field that oscillates parallel to this axis can pass through; light oscillating perpendicular to this axis is absorbed.

  • Polarization Mechanisms:

    • Polarization can also occur through reflection (e.g. off glass or a road), causing glare. Polarizing sunglasses help reduce this glare.

  • Applications in Photography:

    • Photographers use polarizing filters to reduce glare in images.

Practice Problems on Polarization

  • Page 28

    • According to Malus's Law, if the angle between the transmission axes of a polarizer and an analyzer is 0°, the intensity of transmitted light is:

      • a) Zero

      • b) Minimum

      • c) Maximum

      • d) Half the original intensity

    • Answers:

    1. c) Maximum

    2. b) I₀/2

    3. c) I/4

Reflection from Mirrors

  • Page 51

    • Practice Problem Examples:

    1. A light ray strikes a smooth, flat mirror with an angle of incidence of 35°. What is the angle between the reflected ray and the mirror's surface?

      • a) 35°

      • b) 55°

      • c) 70°

      • d) 90°

    2. Which statement is always true regarding ray diagrams?

      • a) The incident ray and reflected ray are perpendicular to each other.

      • b) The incident ray, reflected ray, and normal all lie in different planes.

      • c) The angle of incidence is equal to the angle of reflection.

      • d) The angle of incidence is twice the angle of reflection.

    3. When two mirrors are placed at a right angle to each other, if a light ray strikes the first mirror at an angle of incidence of 25°, the angle of reflection from the second mirror is:

      • a) 25°

      • b) 65°

      • c) 90°

      • d) 115°

    • Answers:

    1. b) 55°

    2. d) The incident ray, mirrored ray, and normal all lie in the same plane.

    3. b) 65°

Concave Mirrors and Their Applications

  • Uses of Concave Mirrors:

    • Everyday:

      • Shaving/Makeup Mirrors: Produce magnified, upright images.

      • Torches & Headlights: Bulbs at focus create parallel light beams.

      • Solar Cookers: Concentrate sunlight for cooking.

    • Scientific:

      • Telescopes: Collect and focus light from stars.

      • Dental/ENT Mirrors: Provide magnified views.

      • Microscopes: Used to focus light on specimens.

    • Industrial:

      • Solar Power Plants: Concentrate sunlight to generate electricity.

      • Satellite Dishes: Focus weak radio signals from satellites.

Practice Problems on Concave Mirrors

  • Page 68

    • Practice Problem Examples:

    1. What is the primary cause of spherical aberration in a concave spherical mirror?

      • a) Different colors of light focus at different points.

      • b) Marginal rays focus at a different spot than paraxial rays.

      • c) The mirror absorbs too much light.

      • d) The image becomes magnified unevenly.

    2. How is spherical aberration corrected?

      • a) Use a parabolic mirror instead.

      • b) Place a convex lens in front.

      • c) Silver the mirror surface.

      • d) Increase the focal length.

    • Answers:

    1. b) Marginal rays focus at a different point than paraxial rays.

    2. a) By using a parabolic mirror instead of a spherical one.

Light Behavior and Optics

  • Refraction Definition:

    • The bending of light as it passes from one medium to another.

  • Index of Refraction (n):

    • Defined as the speed of light in a vacuum divided by the speed of light in the medium: n=cvn = \frac{c}{v}

    • Where:

      • cc = speed of light in a vacuum

      • vv = speed of light in the medium

Practice Problems on Refraction

  • Page 105

    • Practice Problem Examples:

    1. How is the index of refraction (n) defined?

      • a) Speed of light in the medium divided by speed in vacuum.

      • b) Speed of light in a vacuum divided by speed in the medium.

      • c) Wavelength of light in the medium divided by its wavelength in a vacuum.

      • d) Frequency of light in the medium divided by frequency in a vacuum.

    • Answers:

    1. b) The speed of light in a vacuum divided by the speed of light in the medium.

Eye and Lens

  • Nearsightedness (Myopia):

    • Occurs when the eyeball is too long, causing the image to focus in front of the retina.

  • Farsightedness (Hyperopia):

    • Difficulty seeing near objects clearly, often due to a shorter than normal eyeball.

  • Corrective Lenses:

    • Convex lenses converge light rays to aid hyperopia.

    • Concave lenses diverge light rays to assist with myopia.

Practice Problems on Eye and Lens

  • Page 130

    • Practice Problem Examples:

    1. What is the primary cause of nearsightedness?

      • a) Eyeball too short.

      • b) Eyeball too long.

      • c) Weak lens.

      • d) Irregular cornea.

    • Answers:

    1. b) The eyeball is too long, causing the image to focus in front of the retina.