Explanation

When a wave passes from one medium to another, its frequency remains unchanged.

However, its speed, wavelength, and direction may change.

Explanation

Security scanners used at night typically employ infrared (IR) technology to detect heat signatures, allowing for nighttime surveillance.

IR waves have a longer wavelength than visible light, making them ideal for detecting heat radiation from objects or people.

Explanation

Electromagnetic waves are typically listed in order of increasing wavelength (or decreasing frequency) as follows:

• Gamma-rays (shortest wavelength, highest frequency)
• X-rays
• Microwaves (longer wavelength, lower frequency)

Explanation

The correct answer is: Light waves, Radio waves, Microwaves

This group consists only of electromagnetic waves, which are waves that propagate through the electromagnetic field.

They do not require a physical medium to propagate.

Explanation

The velocity of light in a diamond is reduced due to the refractive index of the diamond. The refractive index (n) is related to the velocity of light (v) by the formula:

v = c / n

where c is the speed of light in vacuum (approximately 3x10^8 m/s).

Given the refractive index of diamond is 2.5, we can calculate the velocity of light in diamond as:

v = c / n = 3x10^8 m/s / 2.5 = 1.2x10^8 m/s

So, the correct answer is 1.2x10^8m/s!

Explanation

X-rays are a type of electromagnetic radiation that are commonly used in radiotherapy to destroy cancer cells.

They have enough energy to penetrate deep into tissue and damage the DNA of cancer cells, slowing their growth or killing them.

Explanation

Gamma-rays have the highest penetrating power, making them suitable for treating tumors that are deep inside the body.

Gamma-rays are high-energy electromagnetic waves with frequencies higher than X-rays, and they can travel several centimeters into tissue before being absorbed.

Explanation

Sound waves require a physical medium, such as air, water, or solid objects, to propagate.

They cannot travel through a vacuum because there are no particles to transmit the energy.

Explanation

An echo is caused by the reflection of sound waves off a surface or object.

When sound waves reach a surface, some of the energy is reflected back, creating an echo.

This reflected sound wave then travels back to the listener, arriving later than the original sound, causing the echo effect.

Explanation

Ultrasound has several medical applications, including:

• Pre-natal scanning
• Diagnostic imaging
• Cancer treatment

In industry, ultrasound is used for:

• Cleaning and deburring
• Welding and bonding
• Non-destructive testing