What happens to an electromagnetic wave when it encounters an obstacle?
A Polarization
B Diffraction
C Reflection
D Absorption
Diffraction occurs when an electromagnetic wave encounters an obstacle or aperture. The wave bends around the edges of the obstacle, resulting in a spread-out pattern behind it. This phenomenon is more pronounced with longer wavelengths.
Which equation describes the behavior of electromagnetic waves?
A Ampere’s law
B Faraday’s law
C Gauss’s law
D Maxwell’s equations
Maxwell’s equations describe how electric and magnetic fields interact and propagate as electromagnetic waves. These fundamental equations govern the behavior of electromagnetism, including wave propagation, reflection, and diffraction.
What is the primary function of an antenna in a communication system?
A Polarization
B Transmission
C Reflection
D Amplification
Antennas are used to transmit and receive electromagnetic waves in communication systems. They convert electrical signals into electromagnetic waves for transmission or convert received electromagnetic waves back into electrical signals.
In wave propagation, what happens to the wavelength of a wave as its frequency increases?
A Becomes constant
B Increases
C Decreases
D Stays same
According to the wave equation, as the frequency of an electromagnetic wave increases, its wavelength decreases. This relationship is governed by the formula c=λ×f, where c is the speed of light, λ is the wavelength, and f is the frequency.
What is the effect of diffraction on electromagnetic waves?
A Polarization
B Wave bending
C Speed change
D Frequency shift
Diffraction causes waves to bend and spread when they encounter obstacles or pass through openings. This behavior is more noticeable when the wavelength of the wave is comparable to the size of the obstacle or aperture.
What happens when an electromagnetic wave is transmitted through a medium with higher refractive index?
A Wave bends toward normal
B Wave bends away from normal
C Wavelength increases
D Speed increases
When an electromagnetic wave passes from one medium to another with a higher refractive index, its speed decreases, and the wave bends toward the normal line. This phenomenon is described by Snell’s law.
What does the electric field represent in an electromagnetic wave?
A Magnetic flux
B Magnetic interaction
C Wave propagation
D Force on charge
The electric field in an electromagnetic wave exerts a force on charges, which is responsible for the transfer of energy. It oscillates perpendicular to the magnetic field and the direction of wave propagation.
In the electromagnetic spectrum, which wave has the shortest wavelength?
A X-rays
B Gamma rays
C Microwaves
D Radio waves
Gamma rays have the shortest wavelengths in the electromagnetic spectrum. They also have the highest frequencies and energy levels, which make them highly penetrating.
Which of the following best describes waveguides used in microwave communication?
A High impedance
B Reflective surface
C Energy absorption
D Directional transmission
Waveguides are structures that guide electromagnetic waves in a particular direction. They are used to direct high-frequency waves, such as microwaves, through a defined path with minimal loss.
What is the primary characteristic of a resonant cavity in electromagnetic wave systems?
A Wave enhancement
B Wave reflection
C Frequency control
D Wave absorption
A resonant cavity is designed to support electromagnetic waves at specific resonant frequencies. These cavities are used to control and enhance the frequency of the waves for various applications like lasers and oscillators.
What is the unit of magnetic flux density?
A Ampere
B Tesla
C Volt
D Weber
The unit of magnetic flux density is the tesla (T), which measures the strength of the magnetic field. One tesla represents one weber of magnetic flux per square meter.
Which phenomenon occurs when a wave strikes a surface at an angle greater than the critical angle?
A Total internal reflection
B Diffraction
C Absorption
D Refraction
When a wave strikes a surface at an angle greater than the critical angle, total internal reflection occurs. This happens when the wave is completely reflected back into the medium, with no transmission through the boundary.
What type of wave is used in optical fiber communication?
A Infrared waves
B Microwaves
C Radio waves
D Light waves
Optical fibers use light waves, which are guided through the fiber due to total internal reflection. This allows for high-speed, long-distance communication with minimal loss.
What does the Poynting vector represent in electromagnetic wave theory?
A Electric potential
B Magnetic field strength
C Energy flux direction
D Electric field strength
The Poynting vector represents the direction and magnitude of energy flow in an electromagnetic wave. It is calculated as the cross product of the electric and magnetic fields, indicating the flow of energy.
How does polarization affect the transmission of electromagnetic waves through certain materials?
A It limits wave direction
B It affects amplitude
C It changes frequency
D It slows down wave speed
Polarization restricts the orientation of the electric field in electromagnetic waves. This can affect how waves are transmitted through certain materials, such as polarizing filters or antennas, by blocking certain orientations of the electric field.