Physics Module 6 Flashcards
What is the incident ray?
The incoming ray of light
What is the reflected/refracted ray?
The outgoing ray of light
What is the normal?
A line drawn at a right angle to the reflective/transparent surface
What is the angle of incidence?
The angle between the incident ray and the normal
What is the angle of reflection/refraction?
The angle between the reflected/refracted ray and the normal
What are the two laws of reflection?
- The angle of incidence is equal to the angle of reflection
- The incident ray, the reflected ray and the normal all lie in the same plane
How do images appear in a plane mirror?
Laterally inverted (flipped)
What is a real image?
An image formed by rays of light focusing (converging) to a single point and being projected onto a surface
What is a virtual image?
An image formed by extrapolated rays of light that are not formed physically by rays. It cannot be formed on a screen.
What are the rules for the size and position of an image in a mirror?
- Image the same size as object
- Image same distance from mirror as object
- A line joining the object and image would pass through the mirror at a right angle
What is refraction?
The bending of light as it travels at a different speed through a different medium
If the transparent material has parallel sides, how does the light emerge?
Parallel to its original direction
If the transparent material does not have parallel sides, how does the light emerge?
Deviated (different to its original direction)
How do you define the refractive index of a material?
- speed of light in a vaccum / speed of light in the medium
OR - sin (angle of incidence) / sin (angle of refraction)
What happens to white light when it refracts through a prism?
It disperses into a spectrum
What is total internal reflection?
When light hits the inside of a transparent material at an angle greater than the critical angle, and is internally reflected entierly
What happens if a light ray hits the inside of a transparent material at an angle lesser than the critical angle?
The ray splits into a refracted ray and a weaker reflected ray
What happens if a light ray hits the inside of a transparent material at the critical angle?
The ray splits, but the refracted ray only just leaves the surface
What happens if a light ray hits the inside of a transparent material at an angle greater than the critical angle?
There is no refracted ray - the inside of the transparent material acts like a perfect mirror
What are the properties of a convex (converging) lens?
- Thicker in the middle, thinner at the edges
- Rays parallel to the principle axis are bent inwards when they pass through it
- Principle focus is where the rays converge
What are the properties of a concave (diverging) lens?
- Thinner in the middle, thicker at the edges
- Rays parallel to the principle axis are bent outwards
- Principle focus is where the rays appear to diverge from if extrapolated
What is the principle axis?
The ray of light that passes through the centre of a lens at a 90 degree angle
What is focal length?
The distance between the centre of a lens and the principle focus
What are the properties of a real image formed by a convex lens?
- Inverted (upside-down)
- Diminished (smaller than object) if object is far away
- Enlarged (larger than object) the closer the object gets
How can a convex lens create a virtual image?
If an object is closer to the lens than its principle focus an upright, enlarged virtual image is created (magnifying glass)
What kind of image can a concave lens create?
An upright, diminished, virtual image
What are the names the categories of the electromagnetic spectrum, from lowest to highest frequency?
- Radio waves
- Micro waves
- Infrared waves
- Visible light
- Ultraviolet waves
- X-rays
- Gamma rays
What are uses of radio waves?
- Long distance radio broadcasts
- TV broadcasts
What are uses of micro waves?
- Mobile phones
- Wi-Fi
- Beaming TV, data and telephone signals to satellites
- Heating food
What are uses of infrared waves?
- Motion sensors
- Infrared cameras
- Remote controllers for televisions
- Electric heaters
What are uses of visible light?
- Lasers
- Optical fibres (cable TV, high-speed broadband, telephone networks)
What are uses of ultraviolet waves?
- Sterilisation (killing bacteria/germs)
- Fluorescence (glow in the dark ink, bank notes)
What are uses of X-rays?
- Take pictures of inside the body (medical & security checks)
- Reveal flaws inside metal
What are uses of gamma waves?
- Sterilisation
- Killing cancer cells
