Science Fenns K-5Grades K to 5
A table with a microscope, a hand lens, a prism throwing a rainbow on the wall, a spring scale holding a rock and a balance with two pans.

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Lenses, Prisms and Scales

Microscope, spring scale, mirror, prism, balance.

Lesson 2 of 41

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Before we start

Today’s story

Lenses, Prisms and Scales

A spoon will not tell you how heavy a rock is. A ruler will not show you what is inside a drop of pond water. Different jobs need different tools.

Scientists use lenses to see small things and prisms to split light into colors. They use balances and spring scales to measure mass and weight. Each tool gives evidence, and evidence is what science runs on.

Let us meet the tools one by one. Then you get to use them.

See it

Five steps. Every time.

    Hands on

    Tool Tryout

    25 minutes · Do this with a grown-up nearby

    You need

    • Hand lens
    • Spring scale or a small kitchen scale
    • Flat mirror
    • Flashlight
    • Clear glass of water
    • Penny, leaf and a pencil

    Do this

    1. Look at a penny and a leaf with the hand lens. Draw one detail you could not see before.
    2. Hang a small object from the spring scale. Read the number.
    3. Shine the flashlight at the mirror. Find where the beam lands.
    4. Shine the flashlight through the glass of water onto white paper. Look for color at the edge.
    5. Write what each tool helped you see or measure.
    Write or draw: A table with the tool name, what you used it on, and what you observed.

    Watch for: Notice that the lens shows the grain on the penny and the veins on the leaf. Also notice whether the water makes a hint of rainbow.

    Safety: Never look at the Sun through a lens or shine a light into anyone's eyes.

    Same every time

    Three rules

    Rule 1Choose the tool for the question

    A tool that does not fit gives bad evidence.

    Rule 2Handle tools gently

    Lenses scratch and springs stretch out of shape.

    Rule 3Write down what you observe

    Your notes are your evidence.

    Grandpa Fenn’s notebook

    Say it like a scientist

    convex lens
    A lens that is thicker in the middle and makes things look larger.
    prism
    A clear shape that bends light and splits it into colors.
    balance
    A tool that compares the mass of two objects.
    spring scale
    A tool that measures pull, such as the weight of an object.

    Poppy’s quiz

    Six questions

    Tap an answer. Green means right. You will see why.

    Talk about it

    Say it out loud

    • Which tool would you want most on a creek walk? How do you know?
    • Where have you seen a mirror or a lens used at home or on a farm?
    Did you know

    A spring scale on the Moon would read about one sixth of what it reads on Earth, because the Moon pulls less. The rock's mass stays the same.

    Someone who does this

    An optician grinds and fits lenses so people can see clearly.

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