The different colours of light emitted by the LEDs are electromagnetic waves. In a vacuum (free space), all of these waves must have:

• A the same amplitude
• B the same frequency
• C the same speed
• D the same wavelength

When an LED is on and emitting light, it shows that:

• A there must be a current in the circuit
• B there must be alternating current in the circuit
• C there is a fault in the LED
• D a fuse has blown

An LED needs a minimum voltage to make it emit light. A student investigates this minimum voltage using the circuit shown below.

Draw on this

State how a voltmeter should be connected to the circuit to measure the voltage across the LED.

The student records the minimum voltage at which different LEDs emit light:

Determine whether a bar chart or a line graph is more appropriate to display these results. State what should be plotted on each axis.

The student concludes:

"The minimum voltage depends on the wavelength of the light emitted."

Evaluate the student's conclusion using the data in the table and your knowledge of the electromagnetic spectrum.