Topic 14 - Light Flashcards
What is the angle of incidence?
Angle between the incident ray and the normal line.
What is the angle of reflection?
Angle between the reflected ray and the normal line.
What is a concave lens?
A lens that makes parallel rays diverge.
What is a convex lens?
A lens that makes light rays parallel to the principal axis converge at a point.
What is diffuse reflection?
Reflection from a rough surface and thus the light rays are scattered in different directions.
What is the focal length?
The distance from the centre of a lens to the point where light rays parallel to the principal axis are focused, or in a divergent lens, diverge from.
What is the equation for magnification?
The image height / the object height.
What is the normal?
A straight line through a surface or boundary perpendicular to the surface or boundary.
What is an opaque object?
An object that light cannot pass through.
What is the principal focus?
The point where light rays parallel to the principal axis of a lens are focused, or in a diverging lens, divert from.
What is a real image?
An image formed by a lens that can be projected onto a screen.
What is refraction?
The change of direction of a light ray when it passes across a boundary between two transparent substances.
What is specular reflection?
Reflection from a smooth surface. Each light ray is reflected in a single direction.
What is a translucent object?
An object that allows light to pass through, but the light is scattered or refracted.
What is a transparent object?
An object that transmits all the incident light that enters the object.
What is a virtual image?
An image, seen in a lens or mirror, from which light rays appear to come after being refracted by a lens or reflected by a mirror.
What is the law of reflection?
On reflection from a smooth surface, the angle of the reflected ray is equal to the angle of the incident ray.
What is diffuse reflection?
The reflection of light from a surface such that an incident ray is reflected at many angles, rather than one.
What is an incident ray?
A ray pointing towards and striking a surface.
What is dispersion?
Separating colours into a rainbow.
What does light consist of?
Waves.
What is true about reflected and incident waves?
They have the same frequency and travel at the same speed, so have the same wavelength.
What is the normal?
The line perpendicular to the mirror.
What is true about the relationship between the angle of incidence and angle of reflection?
They are equal
What can an image displayed on a screen be described as?
A real image
What is the change in direction of a light ray called?
Refraction
What happens when light enters a more dense medium?
It is refracted towards the normal.
What happens when light enters a less dense medium?
It is refracted away from the normal.
What happens when light travels from air into glass?
It changes towards the normal.
What happens when light moves from glass into air?
It changes direction away from the normal.
What does the colour of light depend on?
The type of light source.
Stars and lamps emit light that has a continuous range of wavelengths across the visible spectrum.
Light sources like lasers and neon lamps emit a narrow range of wavelengths.
What does the colour of an opaque object depend on?
Pigments and range of wavelengths in the incident light.
What is true of a white surface?
It has no pigments so it reflects light of any wavelength.
What is true of a red surface?
It has a pigment that absorbs all colours of light apart from red.
What are transparent objects?
Objects that transmit all incident light that enters the object.
What is a translucent object?
An object that lets light pass through it, but it is scattered or refracted.
What is an opaque object?
An object that absorbs all the light that reaches it. Light is either reflected scattered or absorbed.
What is the principle focus?
The point to which light is focused.
What is a converging lens uses as?
A magnifying glass
What is magnification equal to?
Image height / Object height
What does the position and nature of an image depend on?
The focal length of the lens.
The distance from the object to the lens.
What is the prinicipal axis?
The straight line that passes along the normal at the centre of each lens surface.
What is the distance from the lens to the film equal to?
The focal length of the lens.
