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What produces electromagnetic waves?
Accelerating charges / oscillating electric and magnetic fields.
Which EM wave is used for communication signals?
Radio waves
Who predicted the existence of electromagnetic waves in the 1860s?
James Clerk Maxwell.
State the wave equation.
c=fλ
Are radio waves safe or harmful?
Safe
Can EM waves travel through a vacuum?
Yes, EM waves can travel without a medium.
Which EM wave is commonly used for heating food?
Microwaves
Who experimentally proved Maxwell’s theory in 1887?
Heinrich Hertz.
If light has a wavelength of 500 nm, calculate its frequency.
f=6.0×1014 Hz
Why are microwaves considered safe at low energy?
They have low frequency and cannot ionize atoms.
What makes a wave electromagnetic?
The combination of oscillating electric and magnetic fields.
Which part of the spectrum can cause sunburn?
Ultraviolet (UV).
What did Hertz produce and detect in his experiments?
Radio waves.
A photon has a wavelength of 600 nm. What is its frequency?
f≈5.0×1014 Hz
Which part of the spectrum can excite molecules and damage DNA?
Ultraviolet light
What determines the classification of EM waves?
Wavelength and frequency.
Which two types of EM waves are ionizing and can cause cancer?
X-rays and Gamma rays.
Maxwell’s theory suggested EM waves travel at what speed?
Speed of light (3.0×108 m/s)
The frequency of an X-ray is 1.07×1019 Hz. What is its wavelength?
λ≈2.8×10-11m
What determines the energy of EM waves?
Frequency ( E=hf )
What is the universal speed of all EM waves in a vacuum?
3.0×108m/s.
Arrange these waves in order of increasing frequency: Radio, Visible, Gamma.
Radio → Visible → Gamma.
How are Hertz’s experiments connected to modern communication?
They led to the development of radio technology.
A radio station broadcasts at 91.5 MHz. Calculate its wavelength
λ≈3.28m
What is the harmful energy threshold for ionizing radiation?
Around 10-19 to 10-17 J per photon