Electromagnetic Spectrum

Step 1: Understanding the Concept:
Velocity of light in a medium: .

Step 2: Detailed Explanation:


Step 3: Final Answer:
.

Concept: All electromagnetic waves travel with the same speed in vacuum.

Step 1: Nature of radiations.
Gamma rays, X-rays and visible light are electromagnetic waves.

Step 2: Speed in vacuum.


Step 3: Conclusion.

Step 1: Understanding the Concept:
Different molecular motions correspond to different regions of the electromagnetic spectrum.

Step 2: Detailed Explanation:

• Vibrational transitions of atoms and molecules typically occur in the infrared (IR) region. IR spectroscopy is used to study molecular vibrations.
• Electronic transitions (in atoms) produce UV and visible light.
• Rotational transitions produce microwaves.
• Nuclear transitions produce gamma rays. Inner electron transitions produce X-rays.

Step 3: Final Answer:
Molecular vibrations produce electromagnetic radiation in the infrared region.

Concept:
Physics - Electromagnetic Spectrum and Applications.
Step 1: Understand Radar requirements.
Radar (Radio Detection and Ranging) systems require waves that can travel long distances, reflect off metallic objects (like aircraft), and have short enough wavelengths to provide good resolution for detecting specific objects.
Step 2: Analyze Microwaves.
Microwaves have frequencies in the range of 1 GHz to 300 GHz. Because of their shorter wavelengths compared to standard radio waves, they can be focused into narrow beams.
Step 3: Explain the benefit.
Narrow beams are essential for determining the precise direction and distance of an aircraft. Furthermore, microwaves are not easily reflected by the ionosphere, allowing them to pass through the atmosphere effectively.
Step 4: Conclusion.
Due to their ability to be focused into directional beams and their reflective properties, microwaves are the standard choice for radar navigation.

Step 1: Use the equation for threshold wavelength.
The threshold wavelength is related to the work function by the equation: where:
- is the work function,
- is Planck's constant,
- is the speed of light, and
- is the threshold wavelength.

Step 2: Rearrange the equation to find .
Rearrange the equation to solve for :
Step 3: Substitute the known values.
Substitute , , and : Thus, the threshold wavelength is: