P14-Light Flashcards
What is the normal?
It is the line perpendicular to the mirror.
What is the angle of incidence?
It is the angle between the incident ray and the normal.
What is the angle of reflection?
It is the angle between the reflected ray and the normal.
What is the rule surrounding the angle of incidence and reflection?
The angle of incidence=the angle of reflection
How is a virtual image formed?
It is formed at a place where light rays appear to come from after they have been either reflected or refracted.
What is specular reflection?
It is reflection from a smooth surface so parallel light rays are reflected all in the same direction.
What is diffuse reflection?
It is reflection from a rough surface because light is scattered in different directions.
What is refection?
This is a change in direction of the wave, such as water crossing a shallow area and waves travelling through a glass block.
What are the rules surrounding refraction?
A light ray changes direction to the normal when it travels into glass with the angle of reflection becoming smaller than the angle of incidence and changing direction away from the normal when it travels from glass into air.
What is colour?
It is a narrow band of wavelength and frequency, where each side of the bands merge into the adjacent bands. The wavelength of light increases from violet to red across the visible spectrum.
What does the colour of a surface depend on?
It depends on chemicals called pigments in the surface materials. It also depends on the range of wavelengths in the incident light.
How does the colour of a surface work?
A white surface has no pigments, reflecting light of any wavelength away. However, if a book is red for example, it has pigments that absorb all colours apart from red. If you looked at the book in blue light it would look black as it absorbs all the incident light.
What is transparency?
They transmit all the incident light that enters the object, not absorbing any at the surface, letting light travel through the object.
What is a translucent object?
It lets light pass through them, but the light is scattered or refracted due to the internal boundaries changing the direction of the light rays repeatedly.
What is an opaque object?
It absorbs all light that reaches it, reflecting, scattering or absorbing it so no light travels through it.
What is a convex lens?
It makes parallel rays converge to a focus at the principal focus. e.g. magnifying glass
What is a concave lens?
It makes parallel rays diverge(spread out). e.g. short sightedness glasses
What is a focal length?
It is the distance from the centre of the lens to the principal focus.
What is a real image?
An image that can be formed on a screen.
What is the formula for magnification?
Magnification=image height/object height
How can you find the position and nature of an image formed by a lens?
You can draw a ray diagram. (see page 210)
What does the position and nature of an image formed by a lens depend on?
The focal length of the lens and the distance from the object to the lens.
How does a camera work?
For a distant object, the distance from the lens to the film must be equal to the focal length of the lens. The nearer an object is to the lens, the bigger is the distance from the lens to the film.
How is a virtual image formed by a convex lens?
The object has to be between the lens and its principle focus. The image is then formed on the same side of the lens as the object. The image is vertical and upright and larger than the object. e.g. magnifying glass
What is a virtual image?
It is when light rays come together where the image appears to be.
