Review: Unit 9 (Light and Optics)

When a wave enters a material with a higher index of refraction...

Wave speed ​ (a)  

Frequency ​ (b)  

Wavelength ​ (c)  

• decreases
• does not change
• increases

Answer explanation

Knowledge 1: When a wave changes mediums, the frequency does not change but wavelength and wave speed do

Higher index of refraction means a slower speed (v=c/n)

Frequency doesn't change

Since v=λf, a slower speed means smaller wavelength

Angle X must be...

• Bigger than 75 degrees

• 75 degrees

• Smaller than 75 degrees

Answer explanation

Knowledge 2: When light changes mediums, some light can be reflected. The Angle of Reflection = The Angle of Incidence

Angle of Incidence = 75 degrees

Angle of Reflection (x) = 75 degrees

Which path will the light take for each of the following situations?

• Material 2 has a larger index of refraction than Material 1

• B

• Material 2 has the same index of refraction as Material 1

• C

• Material 2 has a smaller index of refraction than Material 1

• A

Answer explanation

Knowledge 3: When light enters a medium with a higher index of refraction, it bends towards the normal line. When light enters a medium with a lower index of refraction, it bends away from the normal line.

A (bends towards normal): n₂ > n₁

B (no bending): n₂ = n₁

C (bends away from normal): n₂ < n₁

Person A and Person B both look at a water glare through two differently oriented filters.

For Person A, the glare is not reduced

For Person B, the glare is reduced

Therefore, the light from the glare must be

• Horizontally polarized

• Vertically polarized

• Both horizontal and vertical (non-polarized)

Answer explanation

Skill 1: Predict the effect of passing different types of light (horizontally vs vertically polarized) through different types of filters (horizontally polarizing vs vertically polarizing)

The glare is reduced for Person B, who has a filter that only lets through vertical light. Therefore, the light must be horizontal.

A wave has a frequency of 3 x 10¹⁶ Hz. What type of wave is it?

Answer explanation

It takes light 3.8 minutes to travel from Venus to Earth. How far away is Venus in meters?

An object appears cyan under white light because it reflects ​ (a)   and absorbs ​ (b)   . When this object is placed under yellow light, which is made up of ​ (c)   , it will appear ​ (d)  

• blue and green
• red
• red and green
• green
• red and blue
• blue
• black

Answer explanation

Skill 4: Determine the color an object will appear when placed under non-white light.

Two of these rays are drawn correctly. Which TWO? SELECT TWO

• A

• B

• C

• D

Answer explanation

Skill 5: Draw a ray diagram of an object placed at a certain distance from a convex lens

Ray 1: Parallel to axis, then through focal point (B)

Ray 2: Straight through center

Ray 3: Through focal point, then parallel to axis (C)

The image formed is ​ (a)  

The image formed is ​ (b)   ​

The image formed is ​ (c)  

• real
• smaller
• inverted
• right-side-up
• larger
• virtual

Answer explanation

Skill 6: Describe the image produced by an object placed at a certain distance from a convex lens

Note: you should also know how to calculate magnification

If you quadruple the distance from a light source, the intensity of the light reaching you will be

• Multiplied by 4

• Divided by 4

• Multiplied by 16

• Divided by 16

• Divided by 8

Answer explanation

Skill 7: Predict the effect of changing distance on light intensity

Intensity has an inverse squared relationship with distance

If distance increase by 4, intensity will decrease by 4², which is 16