The method and the results are on the electromagnetic spectrum lab. Do the analysis yourself first, then check the answers below.
Quick answer: The electromagnetic spectrum is the family of transverse waves that all travel at 3.0 × 10⁸ m/s in a vacuum, from radio waves through visible light to gamma rays. These answers go with the grade 8 science lab on electromagnetic spectrum: the graph, the calculations, the uncertainties and the conclusion explained, for all 8 analysis questions.
These model answers use the sample table above. If you collect your own readings, the exact lux values will differ, but the pattern should match: metal blocks radio waves, and thick opaque materials block visible light and infrared.
From most to least transparent: none, clear plastic, white paper, then cardboard and foil together (both pass 0 %).
Question 4 Cardboard and radio
The cardboard absorbed or reflected the visible light and the infrared, but the radio waves passed through. Radio waves have a much longer wavelength and interact with materials differently, so different parts of the spectrum behave differently.
Question 5 Foil and radio
Metal reflects and absorbs radio waves, so a complete foil covering shields the radio from the signal. An everyday example is poor phone signal in a lift: metal blocks radio waves.
Question 6 Paper and the remote
Paper is thin, so some infrared from the remote passed through even though the visible light was reduced. The TV needs only a small share of the signal to respond, so enough infrared got through.
Question 7 Uncertainty
10 ÷ 310 × 100 = 3.2 %. Take three readings and calculate a mean, and keep the meter still: about 3 %.
Question 8 Predicting tracing paper
Tracing paper is translucent, so expect a reading between the plastic and the paper, such as 500 lux. The remote should work and the radio should stay clear because it is not metal: between 310 and 760 lux, remote works, radio clear.
