16 Questions
What is the characteristic of the motion of an object attached to a spring?
A sine wave with a natural frequency
What is the unit of frequency?
Hertz
What type of wave occurs in the same direction as the wave travels?
Longitudinal wave
What is the speed of electromagnetic waves in air and vacuum?
3 × 10^8 m/s
What is the frequency range of the electromagnetic spectrum?
0.03 Hz to 3 × 10^20 Hz
What is the characteristic of an electromagnetic wave?
Oscillating electric and magnetic fields perpendicular to the direction of the wave
What is the energy density of an electromagnetic wave?
Sum of energy density of electric and magnetic fields
What is the definition of energy?
Ability to do work
What is the unit of irradiance?
Energy per unit time per unit area
Why is it not meaningful to ask about the power a source radiates out along a line?
Because a line has no width
What is the ratio of irradiance to the speed of light?
Radiation pressure
What determines the polarization of light?
The direction of the electric field oscillation
What is the process by which certain frequencies of light are absorbed while others are transmitted?
Selective absorption
Why does the sky appear blue?
Because of the scattering of sunlight by air molecules
What is the unit of radiant intensity?
Watts per steradian
What is the application of radiation pressure in space travel?
Propulsion of spacecraft
Study Notes
Periodic Oscillations and Waves
- A periodic oscillation can be described by a wave, with examples including the motion of an object attached to a spring, which exhibits a sine wave pattern.
- The system has a natural frequency defined by its properties, including the mass of the object and stiffness of the spring.
Physical Properties of Waves
- Frequency (f) is the number of oscillations per second.
- Period (T) is the time to undergo one complete cycle.
- Wavelength (λ) is the distance traveled in one period by a moving wave.
- Amplitude is the maximum displacement from equilibrium.
- Wave speed (v) is equal to λ/T or fλ.
Types of Waves
- Longitudinal Waves: Vibrations occur in the same direction as the wave travels, with examples including sound waves.
- Transverse Waves: Vibrations occur perpendicular to the direction of the wave travel, with examples including light waves and waves on a rope.
Electromagnetic (EM) Waves
- EM waves were described by James Clerk Maxwell.
- EM waves carry or transmit energy through vacuum and matter.
- EM waves consist of oscillating electric field (E) and magnetic field (B).
- E and B are perpendicular to each other and both are perpendicular to the direction in which the wave propagates.
Properties of Electromagnetic Waves
- The speed of EM waves in air and vacuum is c = 3 × 10^8 m/s.
- EM waves can be produced by supplying an alternating current to a vertical wire (antenna), which acts as an oscillating electric dipole.
- The electromagnetic spectrum ranges from 0.03 Hz to 3 × 10^20 Hz.
- Examples of EM waves include radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays.
Energy, Power, and Irradiance
- Energy is the ability to do work.
- Power is energy per unit time.
- Irradiance (I) is energy per unit time per unit area.
Radiation Pressure
- EM waves carry energy and momentum.
- Pressure is defined as the ratio of irradiance to the speed of light.
Polarization
- The direction of the electric field oscillation determines the polarization of the light.
- Examples of polarization include selective absorption, reflection, and molecular scattering.
- The sky appears blue due to the scattering of sunlight by air molecules.
Learn about periodic oscillations, waves, and their physical properties including frequency, period, wavelength, and amplitude.
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