Learning goal: Demonstrate that light travels in a straight line until it strikes an object or enters another medium.
What to know
Light travels outward from a source along straight paths. We use ray lines with arrows as a model of those paths.
We see an object when light from a source reaches it and reflected light then reaches our eyes.
Three aligned holes let a narrow flashlight beam continue straight through. Moving one card blocks the path rather than making the light curve around it.
When light strikes matter, it may be reflected, absorbed, or transmitted. Entering a different medium can also change its direction.
A good demonstration controls the source and card positions and records whether light reaches the screen.
WATCH & NOTICE
Light Sources, Reflection, and Shadows
From Little School
Trace the light path and watch what changes when light meets a material.
Aim a flashlight through holes in three cards toward a screen. Light appears on the screen only when the holes lie along one straight path.
STRAIGHT-LINE LIGHT LAB
Can the beam reach the screen?
Move the middle card. Light reaches the target only when all three holes share one straight path.
Light raya line model showing directionPaththe route light travelsBlockedstopped by an object
Screen
Light reaches the screen. The aligned holes provide evidence of one straight path.
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LESSON 5.2 · SC.3.P.10.4
Reflect, Refract, Absorb
Learning goal: Use a light-path model and evidence to distinguish reflection, refraction, and absorption.
What to know
Reflection occurs when light bounces from a surface. Smooth mirrors produce an orderly reflected path and a clear image.
Refraction occurs when light changes direction as it passes from one medium into another, such as air into water.
Absorption occurs when a material takes in light energy. Dark or dull surfaces often absorb more visible light and may warm.
Transmission means light passes through a material. A material can transmit some light while reflecting or absorbing some too.
Name the interaction from evidence: a returning ray suggests reflection, a bent path suggests refraction, and a weakened or missing ray with warming can suggest absorption.
WATCH & NOTICE
Light Sources, Reflection, and Shadows
From Little School
Trace the light path and watch what changes when light meets a material.
A mirror redirects a flashlight spot, a straw appears shifted at the water surface, and black paper produces little reflected light because much of it is absorbed.
LIGHT BEHAVIOR LAB
What happens when the ray meets matter?
Change the material and trace the arrows. Use the path—not the object's name—to identify the interaction.
Reflectbounce back from a surfaceRefractchange direction in a new mediumAbsorbtake in light energyTransmitallow light to pass through
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•••
Reflection
The ray returns from the mirror. Its direction changes at the surface.
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LESSON 5.3 · SC.3.P.10.3 · SC.3.P.10.4
Light and Shadows
Learning goal: Explain how straight light paths, material type, and position determine a shadow.
What to know
A shadow forms on a surface where an object blocks light traveling from a source.
Opaque materials block most light and make dark shadows. Transparent materials transmit most light; translucent materials transmit some and create faint or blurry shadows.
With a spreading light source, moving an object closer to the light usually makes its shadow larger; moving it toward the screen makes the shadow smaller and sharper.
The shadow has the outline of the object from the light's direction, but it does not show the object's color.
A fair shadow investigation changes one factor—distance, material, or orientation—while keeping the others the same.
WATCH & NOTICE
Light Sources, Reflection, and Shadows
From Little School
Trace the light path and watch what changes when light meets a material.
Hold the same shape between a flashlight and a wall. Slide it toward the flashlight and measure the growing shadow, then compare opaque cardboard with translucent paper.
INTERACTIVE SHADOW LAB
Change distance and material
Move the object between the flashlight and wall, then change what it is made from. Observe shadow size and darkness.
Opaqueblocks most lightTranslucentpasses some lightTransparentpasses most light
★
★Wall
Dark, medium-sized shadow. The opaque card blocks most of the straight light paths.
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Unit 5 benchmark map
Crystal Lake’s unit outline is mapped to Florida’s official Grade 3 science course. Lessons group connected ideas so benchmarks are learned in context.
SC.3.P.10.3Light Travels StraightSC.3.P.10.4Reflect, Refract, AbsorbSC.3.P.10.3 · SC.3.P.10.4Light and Shadows