Physics - Plane Mirror Quiz

Actual Path of Light

The path in front of the mirror, shown as a solid line.

Apparent Path of Light

The path behind the mirror, shown as a dashed line.

Normal Line

Path perpendicular to the mirror, represented as a dashed line. It is drawn where the path of light hits the mirror.

Law of Reflection

When light reflects off a surface, the angle of reflection is equal to the angle of the incidence. “Angle in = angle out”.

Parallax

The difference in the apparent position of an object when viewed along different lines of sight. Can be used to determine relative distances from an observation point.

• Astronomers can use parallax to tell which stars are closer to us than others.

Depth Perception

Our brains interpret the differences in the images seen by each eye to map out the relative distances of objects around us.

Properties of Light

• Light travels at 3.00 × 10⁸ m/s.

• Light travels in straight lines called rays.

• Because of this, our brains interpret reflected light as having traveled in a straight line, even when it hasn’t, creating virtual images.

Virtual Images

Formed by the apparent path of light (meaning that light doesn’t actually go there).

Colors of Light

Primary Colors/Additive: Red, Green, Blue

Subtractive: Yellow, Cyan, Magenta

White Light vs. Black Light

• White light is made up of all visible colors of light.

• Black light is really the absence of any light.

Reflection and Color

• White objects reflect all colors of light.

• Black objects reflect no light, absorbing all colors. (Most black objects still reflect some light, normally around 5%, otherwise we wouldn’t see them at all.)

• Red objects reflect only red light, absorbing all others. Same thing for every other color.

Regular Reflection

Preserves an image (mirrors).

• Regular reflections from mirrors reflect about 96% of the light

Diffuse Reflection

Doesn’t preserve an image. (Most reflections are diffuse).

• Diffuse reflections can also reflect a large percentage of light, depending on the type and color of the surface.

Light Transmission

When light passes through a substance.

• Translucent: Image is not preserved.

• Transparent: Image is preserved.

Opaque

When light does not pass through a substance.