Light Revision Flashcards
(24 cards)
What is light?
Light is a form of electromagnetic radiation that travels in straight lines and allows us to see.
What speed does light travel at in a vacuum?
Approximately 300,000 km/s (or 3 x 10⁸ m/s).
What are luminous objects?
Objects that produce their own light (e.g., the Sun, a lightbulb).
What are non-luminous objects?
Objects that do not produce light but can reflect it (e.g., the Moon, a book).
What is the law of reflection?
The angle of incidence equals the angle of reflection.
What is the angle of incidence?
The angle between the incoming ray and the normal line.
What is the angle of reflection?
The angle between the reflected ray and the normal line.
What is a normal line in reflection?
A line drawn at 90° to the surface at the point of incidence.
What type of surface gives a clear reflection?
A smooth and shiny surface like a mirror.
What is refraction?
The bending of light when it passes from one medium to another (e.g., air to glass).
Why does light bend during refraction?
Because it changes speed when moving between materials with different densities.
What happens to light when it enters a denser medium (like air to glass)?
It slows down and bends towards the normal.
What happens to light when it exits to a less dense medium (like glass to air)?
It speeds up and bends away from the normal.
What is a convex lens?
A lens that curves outward and converges light rays to a point (used to correct hyperopia).
What is a concave lens?
A lens that curves inward and diverges light rays (used to correct myopia).
What is myopia?
Also called short-sightedness. The eye focuses light in front of the retina, so distant objects appear blurry.
How is myopia corrected?
With a concave lens, which diverges the light rays before they enter the eye.
What is hyperopia?
Also called long-sightedness. The eye focuses light behind the retina, so close objects appear blurry.
How is hyperopia corrected?
With a convex lens, which converges the light rays sooner.
Why is the image formed on our retina upside down?
The convex lens in our eye flips the image. Our brain processes it and turns it the right way up.
Why can’t we see light bending during refraction with the naked eye?
Because the change in direction is usually small unless it’s a strong difference in material density.
What causes a rainbow?
Refraction, dispersion, and reflection of light in water droplets split white sunlight into its colors.
What is total internal reflection?
When light hits a boundary at a large angle and reflects completely back into the medium (e.g., in fiber optics).
What’s the critical angle?
The minimum angle of incidence at which total internal reflection occurs.
