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8th grade · Science · Unit 1 of 7

Light & Radiation

Waves, the spectrum and how light behaves

What your child practices

Wavelength and frequency, the electromagnetic spectrum from radio waves to gamma rays and what each is used for, reflection, refraction and color, and staying safe from UV radiation.

Alaska content standards learning standard: MS-PS4-1; MS-PS4-2 · wave properties and how light reflects, refracts and is absorbed

How we explain it

Children can open this short lesson before they practice.

  1. The electromagnetic spectrum, from longest to shortest wavelength: radio, microwave, infrared, visible light, ultraviolet, X-ray, gamma.
  2. Shorter wavelength means higher frequency and more energy.
  3. Light reflects off mirrors and bends (refracts) when it passes into a new material. Block UV with sunscreen and shade.

Example: Which has a longer wavelength: radio waves or X-rays? Radio waves are at the long end of the spectrum. X-rays are near the short end. Answer: radio waves

Light & Radiation in Alaska

In the Alaska content standards, this is unit 1 of 7 in 8th grade Science, before Motion, Forces & Newton’s Laws.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: Alaska Department of Education and Early Development

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    As the frequency of a wave increases, its wavelength…

    • stays the same
    • disappears
    • decreases
    • increases

  2. Question 2

    Light can act as both a wave and a stream of particles. What are the particles called?

    • protons
    • electrons
    • photons
    • neutrons

  3. Question 3

    Which type of radiation is used to heat food in a microwave oven?

    • microwaves
    • gamma rays
    • X-rays
    • ultraviolet

  4. Question 4

    Light is a form of…

    • sound energy
    • electromagnetic radiation
    • matter
    • heat only

  5. Question 5

    Why do we see white light split into colors in a prism?

    • Different colors bend by different amounts when they refract.
    • The prism adds paint.
    • Light changes into sound.
    • The prism makes new light.

  6. Question 6

    Put these types of electromagnetic radiation in order from the longest wavelength to the shortest.

    • 🌈Visible light
    • 🍿Microwaves
    • 🩻X-rays
    • ☀️Ultraviolet

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