Which item normally produces its own visible light when switched on?
- An unlit book
- A torch
- A wooden ruler
Answer and explanation
A torch
A working torch is a light source; the ruler and book are normally seen by reflected light.
Subjects
Light & optics
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Make a worksheet900 question instances
Sample exercises
What makes a shadow behind an opaque card?
- The card blocks some light.
- The card sends out darkness.
- The card removes gravity.
Answer and explanation
The card blocks some light.
A shadow is a region reached by less direct light.
Which sequence explains seeing a red book in a lit room?
- Eye → book → lamp
- Book → gravity → eye
- Lamp → book → eye
Answer and explanation
Lamp → book → eye
Light illuminates the book and some reflected light reaches the eye.
Which material usually lets you see a clear image through it?
- Thick cardboard
- Clear window glass
- A wooden board
Answer and explanation
Clear window glass
Clear glass transmits visible light with relatively little scattering.
Explain why a shadow can move even when the object stays still.
Answer and explanation
The light source can move, changing which paths are blocked.
Accept a change in source position or direction with a coherent explanation.
How could you compare two materials' ability to pass light fairly?
Answer and explanation
Use the same light, distance and background, and change only the material.
Credit controlling the light and geometry rather than judging different setups.
Study notes
Light, seeing and shadows
Follow light from a source to an object and understand blocked light.
Grades 1–3Light, seeing and shadows · Revision sheet
Follow light from a source to an object and understand blocked light.
Grades 1–3Reflection and the normal
Measure angles from a perpendicular reference line, not from the mirror.
Grades 7–10Reflection and the normal · Revision sheet
Measure angles from a perpendicular reference line, not from the mirror.
Grades 7–10Refraction and critical conditions
Track speed, wavelength and angle while frequency stays tied to the source.
Grades 9–12Refraction and critical conditions · Revision sheet
Track speed, wavelength and angle while frequency stays tied to the source.
Grades 9–12Thin lenses and image conventions
Use one sign convention and avoid claims that every convex lens image is real.
Grades 10–12Thin lenses and image conventions · Revision sheet
Use one sign convention and avoid claims that every convex lens image is real.
Grades 10–12Refraction using given sine values
Angles are measured from the normal. Find the sine requested, not an angle in degrees.
Grades 10–12Light speed in a medium
The refractive index is dimensionless; use the given vacuum speed.
Grades 10–12Image distance for a converging lens
This model uses a thin lens, a real object beyond the focal point, and positive real-image distances.
Grades 11–12Image-size magnification
This question asks for size, not orientation; the magnification magnitude is given.
Grades 10–12Light & optics · Formula reference
Formula reference
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