Light - Form Two Physics

Flashcards about Light

What is light?

Light is a form of energy that the eyes can detect.

What are luminous objects?

Objects that give off light.

What are reflectors?

Objects that reflect light from another source.

What is the speed of light?

300,000,000 m/s or 300,000 km/s.

What can light undergo when incident on a surface?

Transmission, reflection, refraction, diffraction, adsorption, and scattering.

How are shadows formed?

When light rays from a source are blocked.

What is reflection of light?

The process whereby light rays bounce off the surface of an object on which they fall.

What are the 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 on the same plane.

What are good reflective materials?

Smooth, shiny surfaces and are usually pale colors; Give clear images because they reflect light regularly; Mirrors.

What are bad reflective materials?

Rough, matt surfaces and are usually dark colors; Give no or diffuse images because they reflect the light irregularly.

What are transparent materials?

Materials that allow light to pass through them without being scattered or absorbed, allowing us to see clearly through them.

What are translucent materials?

Materials that allow light to pass through them but change the direction of the rays, so objects are not seen clearly.

What are opaque materials?

Materials that stop all light from passing through.

What are plane mirrors?

Flat mirrors that give non-distorted lifelike images.

What is a concave mirror?

A mirror that curves inwards.

What is a convex mirror?

A mirror that curves outwards.

What kind of image do you see when you look at a mirror?

Virtual image, same size as the original object, and the same distance behind the mirror as the object is from the mirror.

What is lateral inversion?

When something is reflected in a plane mirror, left becomes right and right becomes left.

How do we see things?

When light enters our eyes either directly from the source or from an object which reflects light.

What causes the bending of light or refraction?

The speed of light waves depends on the material they are travelling through. If light waves enter a different material, the speed changes, causing the light to bend.

What is refraction?

The change in the direction of light as it passes from one medium to another, accompanied by a change in speed and wavelength.

What are the rules of refraction?

Light rays passing from a less dense medium to a more dense medium always bend towards the normal, and light rays passing from a more dense to a less dense medium always bend away from the normal.

What is dispersion?

A prism splits a ray of white light into a spectrum of colors.

What are the three primary colors of light?

Red, green, and blue.

What are the secondary colors of light?

Magenta, yellow, and cyan.

Why does a red snooker ball look red in white light?

The snooker ball absorbs all the colors of the spectrum except red. Only red light is reflected into your eye, so the snooker ball appears red.

Why does a green snooker ball look green in white light?

The snooker ball absorbs all the colors of the spectrum except green. Only green light is reflected into your eye, so the snooker ball appears green.

Why does a black snooker ball look black in white light?

The snooker ball absorbs all the colors of the spectrum. No light is reflected into your eye, so the snooker ball appears black.

Why does a white snooker ball look white in white light?

The snooker ball does not absorb any of the colors of the spectrum. The whole spectrum of light is reflected into your eye, so the snooker ball appears white.

Summarize Key Concepts about light.

The image in a plane mirror is laterally inverted, the same size and has the same distance as the object; angle of incidence (i) = angle of reflection (r); happens because the light changes speed and bends in different media; when light enters a more dense medium , it bends towards the normal. In reflection: i = r In refraction: i ¹ r