An object can be seen if four conditions are met: there is an object, an eye, a source of light, and a direct path between the object and the eye.
Light must enter the eye or sensor to be seen or detected.
The brighter an object appears, the more light that reaches the eye or detector from it.
Light travels in straight lines.
Light continues traveling until it reaches an object that scatters or absorbs it.
A shadow is formed behind an object that blocks the path of light.
A shadow is seen by detecting that less light reaches the eyes from it than from the area surrounding it.
Content Knowledge:
Lesson 1
Four conditions need to be met for an object to be seen
an object,
an eye,
a source of light, and a direct,
unblocked path between the object and the eye
Lesson 2
Some students can see an object, while others cannot because of their position in the room.
Properties of light
Lesson 3
Light is continuously emitted in all directions from a light source and travels in straight lines.
Some light travels directly to the eye if there is an unblocked path.
Some light bounces off an object and travels to the eye, if there is an unblocked path.
Light travels in all directions in three-dimensional space. Two-dimensional diagrams can only depict rays on the plane of the paper.
Light is emitted in all directions from each point of a light source. Rays are shown to emanate in all directions from the light source in general, not from each point in the light source.
Lesson 4
How the eye works:
The eye has a clear opening, called the pupil, that lets light through. In the photograph of the eye, the pupil is the black circle in the center of the eye. The eye is a covered opening—not a hole in the eye.
Sensors located at the back of the eye (the retina) sense light that reaches them and generate an electric signal, which is sent to the brain through the optic nerve. When a person sees a light bulb, some of the light from the bulb enters the eye and reaches the retina, which transmits an electrical signal to the brain. The brain identifies the signal as being produced by the light from a light bulb.
Probes measure the light intensity with the unit of lux
candle = 0–2.6lux
light bulb = 0–260lux
sun = 0–26,000lux
Lesson 5
Shadows and what happens when an object blocks the path of light.
The shape of a shadow depends on the shape of the object
Scattering occurs when light bounces off an object in all directions. This occurs when the surface of the object is rough and unpolished.
Reflection occurs when light bounces off an object only in a certain direction. This occurs when the surface of the object is smooth and polished.
A reflection of one object is seen in a second object only if the second object reflects light, not if it scatters it.
Some objects are transparent and let light pass through them.
When light reaches an object, it is scattered (or reflected), transmitted, absorbed, or some combination of these.
Light can make things happen when it is absorbed.
Content Knowledge:
Lesson 6
Reflection and scattering of light
The law of reflection is that the angle of incidence equals the angle of reflection
Difference between the ways light bounces off a mirror and off a wall.
Lesson 7
Transparency
Translucency
Transmission
Some objects are transparent and let light pass through them
Lesson 8
Absorption
When different colored lights are mixed, they appear as a new color, brighter than the original colors.
White light is a mixture of all colors of light—it is the brightest color. Black is the color associated with the absence of light.
Filters color light by absorbing certain colors and transmitting the rest.
Colored objects scatter only certain colors of light and absorb the rest.
Content Knowledge:
Lesson 9
Light makes things happen (connection to energy)
Mixing different colors of light is not the same as mixing the same colors of paint. When colors of light are mixed, nothing new is created. The combination just appears like a new color
Light comes in many different wavelengths, and the eyes perceive the different wavelengths as different colors
When more light reaches the eyes, we interpret the object we are looking at as being b righter.
Lesson 10
The speed of light changes when it passes from one medium to another. This change in speed can cause light to change direction. This phenomenon is known as refraction.
When traveling through a medium, the speed of light is slightly different for the various colors of light. Only in a vacuum is it the same for all of them. When multicolored (polychromatic) light goes from one medium to another, the different colors change speed differently. This makes each color change direction differently. Since each color moves now in a different direction, they start moving away from each other. This phenomenon is called color dispersion.
A prism compounds the effect of color dispersion. Light passing through a prism goes through a medium change twice: once when entering the prism and once when leaving it. The faces of the prism are built at an angle to each other so that the refraction of the light at each surface happens in the same direction rather than in opposite directions, thus reinforcing each other.
Students may know the mnemonic ROY G BIV, which stands for the colors of light in the visible spectrum
Lesson 11
With the evidence collected throughout the unit, students should be able to give a full explanation of how they saw the optical illusions from the start of the unit and a new optical illusion they will see now.