absorbtion
The blackness of the type on a page is due to _________.
Incident light makes the electrons oscillate. The electrons then emit light or absorb the light and convert it to heat.
How does incident light that falls on an object affect the motion of electrons in the atoms of the object?
They reemit more light or collide with neighbors, thereby converting light energy to more internal energy.
What do the electrons affected by illumination do when they are made to vibrate with greater energy?
Light takes the quickest path in going from one place to another.
What is Fermat’s principle of least time?
The angle of incidence equals the angle of reflection.
Cite the law of reflection.
The image is the same distance behind the plane mirror as the object is in front of it.
Relative to the distance of an object in front of a plane mirror, how far behind the mirror is the image?
Yes. The mesh of a radio dish is polished for long wavelength radio waves and yet rough for short wavelength light waves.
Can a surface be considered polished for some waves and not for others? Cite an example.
a mirror
Specular reflection is common in the light reflected from _________.
When the light strikes the glass in one medium (such as air) and exits the glass in another medium (such as water)
When is the angle at which a ray of light strikes glass not the same as the angle it exits?
Yes. It is as if the curved mirror is made of many small plane mirrors at slightly different orientations to each other.
Does the law of reflection hold for curved mirrors? Explain.
Refraction. Light curves through warm, low-density air near the ground, where it travels faster.
Is a mirage the result of reflection or refraction? Why does it happen?
The light oscillates electrons in the atoms of the glass or water. The electrons absorb some of the energy and reemit it after a delay at each atom.
When the wheel of a cart rolls from a smooth sidewalk onto a plot of grass, the interaction of the wheel with the blades of grass slows the wheel. What slows light when it passes from air into glass or water?
Thinner. Light bends more entering high index of refraction materials.
Are eyeglasses made with “high index of refraction” materials thinner or thicker? Why?
Violet light travels slower because it is closer in frequency to the ultraviolet resonance of the atoms in the glass.
Which travels more slowly in glass, red light or violet light? Why?
The minimum angle of incidence inside a medium where light is totally reflected
What is meant by critical angle?
When two parallel rays of light pass through a converging lens, the rays bend towards each other. When they pass through a diverging lens, the rays move apart from each other.
Distinguish between a converging lens and a diverging lens.
less than the speed outside the material
Total internal reflection occurs when the speed of light in a material is _________.
A virtual image, unlike a real image, cannot be displayed on a screen. A virtual image is upright, whereas a real image is inverted.
Distinguish between a virtual image and a real image. Mention in each case whether the image made by a single lens is right-side up or inverted.
is inverted
A feature of a pinhole camera is that the image _________.
