Chapter 26 & 27 color and light
Chapter 26: Light
Electromagnetic Waves
Q: What causes light to be emitted?
A: Accelerated motion of electrons.
Q: What are the two components of an electromagnetic wave?
A: Vibrating electric and magnetic fields.
Q: How does the frequency of a wave relate to its energy?
A: Higher frequency means higher energy.
Electromagnetic Spectrum
Q: What part of the electromagnetic spectrum is visible to the human eye?
A: The visible light spectrum (red to violet).
Q: Which type of electromagnetic wave has the highest energy?
A: Gamma rays.
Q: Why does ultraviolet light cause sunburns?
A: It has higher energy than visible light and can penetrate the skin.
Transparent & Opaque Materials
Q: How does light travel through transparent materials?
A: It is absorbed and reemitted by electrons in the material, slowing down the speed of light.
Q: Why does glass not transmit ultraviolet or infrared light?
A: Glass absorbs these frequencies instead of reemitting them.
Q: What determines if an object appears opaque?
A: If it absorbs light without reemitting it as visible light.
Shadows & Eclipses
Q: What is the difference between an umbra and a penumbra?
A: An umbra is a total shadow, while a penumbra is a partial shadow.
Q: Why do solar eclipses occur?
A: The Moon blocks sunlight from reaching the Earth, creating a shadow.
Seeing Light – The Eye
Q: What part of the eye is responsible for most of the light bending?
A: The cornea.
Q: What is the function of rods and cones in the retina?
A: Rods detect low light, while cones detect color.
Q: What is lateral inhibition in vision?
A: The process where bright areas prevent neighboring areas from appearing as bright, increasing contrast.
Chapter 27: Color
Color Perception
Q: What determines the color an object appears?
A: The frequencies of light it reflects or transmits.
Q: What happens when an object absorbs all visible light?
A: It appears black.
Mixing Light & Pigments
Q: What are the additive primary colors of light?
A: Red, green, and blue (RGB).
Q: What happens when red, green, and blue light are combined?
A: White light is produced.
Q: What are the subtractive primary colors of pigments?
A: Cyan, magenta, and yellow (CMY).
Q: What color will a blue object appear in yellow light?
A: Black, because yellow does not contain blue wavelengths to reflect.
Why the Sky is Blue
Q: Why does the sky appear blue?
A: Shorter wavelengths (blue) are scattered more by small atmospheric particles.
Q: Why does the sky appear whiter on a humid day?
A: Larger particles scatter all wavelengths, creating a whitish appearance.
Why Sunsets Are Red
Q: Why do sunsets appear red?
A: As light travels through more atmosphere, shorter wavelengths scatter away, leaving longer wavelengths like red and orange.
Q: What would happen if the sky scattered orange light instead of blue?
A: Sunsets would appear blue.
Why Clouds Are White
Q: Why do clouds appear white?
A: Water droplets scatter all wavelengths of visible light.
Q: What causes clouds to appear gray or dark?
A: Thicker clouds absorb and scatter more light, reducing the amount that reaches your eyes.
Why Water is Greenish-Blue
Q: Why does water appear blue-green?
A: Water absorbs red light more than blue, leaving mostly blue and green light.
Q: How does glacier runoff make lakes appear vivid blue?
A: Tiny suspended particles scatter light, enhancing the blue color.
Possible Extra Questions for the Test
Q: What is the speed of light in a vacuum?
A: 300,000,000 m/s (or 3.0 × 10⁸ m/s).
Q: How does refraction affect the speed of light in different materials?
A: Light slows down in denser materials like water and glass.
Q: What happens when light passes from air into water at an angle?
A: It bends toward the normal due to refraction.
Q: What is the difference between reflection and refraction?
A: Reflection bounces light off a surface, while refraction bends light as it changes medium.