Light Flashcards
What is light?
is a form of energy that enables us to see things.
Name some sources of luminous objects.
The sun,a bulb, a flame, a star
Give two examples of non-luminous objects.
A desk and a chair
How can we see things?
We can see things because they reflect or emit light coming from them.
What is meant by ‘light travels in straight lines’?
It means that when light comes from an object, it travels straight, which is called rectilinear propagation.
Give two examples where you can observe light traveling in straight lines.
When we see rays coming out from behind clouds,
When sunlight enters a room through ventilators.
How can we sometimes see beams of light?
We can sometimes see beams of light when there is dust or smoke because particles help us to see the path of light.
Explain how shadows are formed.
Shadows are formed when an opaque object blocks the path of light, causing a shadow to form on the opposite side of the object, away from the light source.
What do you mean by a beam of light?
A beam of light is a narrow set of light rays. A group of rays is called a beam or pencil beam.
What are some examples of reflecting surfaces?
A shiny stainless steel,a mirror ,windows, calm water etc
If there’s a mirror and a ray it’s coming towards that ray is called the______ ___. The reflected ray is called the ________ ___
Incident ray. Reflected ray
How is a mirror usually drawn?
With a straight line and lines
Mention instances where periscopes are used.
In a submarine and to watch a football match
Explain how periscopes work.
A periscopes is an optical instrument used to observe above a concealed place. It consists of a tube with mirrors set parallel to each other at a 45 degree angle. The mirrors reflect light from one to another and the observes can see.
What is the distance relationship between an object and its image in a plane mirror?
The distance from the object to the mirror is equal to the distance from the image to the mirror.
List three characteristics of the image formed by a plane mirror.
Three characteristics of the image formed by a plane mirror:
• The image is the same size as the object.
• The image is laterally inverted (left and right are reversed).
• The image is upright (erect).
What type of image is formed by a plane mirror, and why is it called that?
The image formed by a plane mirror is a virtual image. It is called a virtual image because the rays of light do not actually meet but appear to come from behind the mirror.
Explain why the image formed by a plane mirror appears to have depth.
The image appears to come from behind the plane surface of the mirror, giving the illusion of depth.
What is the difference between a real image and a virtual image?
A real image is formed when rays of light actually meet at a point and can be projected onto a screen. A virtual image, on the other hand, is formed when rays of light appear to diverge from a point behind the mirror and cannot be projected onto a screen.
What happens to light when it passes from air into glass?
When light passes from air into glass, it slows down and bends towards the normal.
Define refraction.
Refraction is the bending of light as it passes from one transparent medium to another, changing its speed and direction.
Why does refraction occur?
Refraction occurs because light changes speed when it moves from one medium to another with a different optical density.
How does the speed of light change when it moves from air to a more optically dense medium like glass?
The speed of light decreases when it moves from air to a more optically dense medium like glass.
What is the speed of light in air compared to its speed in glass?
The speed of light in air is approximately 300,000,000 meters per second, while in glass, it is about 200,000,000 meters per second.
