Essential Physics

Section 2 review

Optical devices may change the path of light rays through reflection and refraction. Reflection bounces light off of a surface, such as a mirror. Specular reflection occurs with shiny surfaces and diffuse reflection occurs with nonshiny surfaces, such as paper. Refraction bends the path of light as the light passes from one medium into another, such as from glass into air and vice versa. Refraction is the principle behind prisms and lenses. Both reflection and refraction can be used to form images. Magnification occurs when an image has a different apparent size than an object. Dispersion occurs when an optical element separates white light into its constituent colors, such as a prism creating a rainbow. Optical media may have varying degrees of opacity, transparency, or translucency. Read the text aloud

Read the text aloud

mirror, lens, prism, reflection, refraction, specular reflection, diffuse reflection, magnification, transparent, opaque, translucent

m = \frac{h_{i}}{h_{o}}

Review problems and questions

Match each diagram to the name and function

Match each diagram (A, B, and C) to the appropriate name (i–iii) and function (a–c) from the list.
Name Function
Mirror

Lens

Prism
Refracts light and may magnify.

Reflects light and may show images.

Refracts light without magnification.

A ruler of length 30 cm is submerged in a tank of water. The image seen outside the tank is measured to be 36 cm long.
1. What is the magnification of this system?
2. In centimeters, how long would a meter stick in the tank of water appear to be?

Answer:

1.2
120 cm

Solution:

Asked: magnification m from the tank
Given: length of ruler, h_o = 30 cm; length of the image, h_i = 36 cm
Relationships: m = h_i ⁄ h_o
Solve: $m = \frac{h_{i}}{h_{o}} = \frac{36 cm}{30 cm} = 1.2$ Answer: The magnification of the tank is 1.2.
Asked: height h_i of an image of a meter stick in the tank
Given: magnification of the tank, m = 1.2
Relationships: m = h_i ⁄ h_o, length of a meter stick h_o = 1 m = 100 cm
Solve: $m = \frac{h_{i}}{h_{o}}$ Rearrange and solve for h_i: $h_{i} = m \times h_{o} = 1.2 \times 100 cm = 120 cm$ Answer: A meter stick would appear to be 120 cm long.

A piece of sandpaper may turn a transparent plastic window into a translucent plastic window. Propose a hypothesis to explain why sanding the surface makes the window translucent. Use the concept of light rays in your explanation.

How large does the image of a 10-m-tall tree appear when using an optical device with a magnification of 0.3?

In Investigation 20A on page 586, which optical device would you choose to
1. create a magnified (enlarged) image?
2. create an upside-down or inverted image?
3. create an image the same size as the object?

How should you handle a lens when you pick it up?


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