Explanation

We are told:

• A copper penny is heated to 100 °C.

• Its diameter increases by 0.17%.

• We are to find the percentage increase in the area of one of its circular faces.

Let’s denote:

• Original diameter: $D$
  

• Increased diameter: $D' = D + Delta D = D (1 + 0.0017)$

• Area of a circle: $\mathrm{<br>}$

• New area:

  A′=π(D′)^2​/4=(D(1+0.0017))^2/4π​=A⋅(1+0.0017)^2

Use binomial expansion (for small x):

(1+x)^2≈1+2xwhen x is small

Here, $x=0.0017$, so:

(1+0.0017)^2≈1+2(0.0017)=1+0.0034=1.0034

Thus, the area increases by:

0.34%​

Explanation

Electromagnetic spectrum order (longest to shortest wavelength):

Radio waves (includes TV signals) → Infrared → Visible light → X-rays.

It follows this order, starting with television (radio waves) and ending with X-rays.

Explanation

• The heat from the Sun reaches Earth in the form of electromagnetic waves, which is called radiation.
• This includes ultraviolet (UV) rays, visible light, and infrared (IR) rays.
• Radiation is the transfer of energy through electromagnetic waves, without the need for a medium like air or water.

Explanation

The to and fro movement of a pendulum is called a vibration or oscillation.

It's a repeated back-and-forth motion about a central position.

Explanation

Explanation

When a sound wave strikes a surface and bounces back into the original medium, this is called reflection.

It’s the same principle behind echoes.

Explanation

Polychromatic light contains multiple wavelengths or colors of radiation.

It is the opposite of monochromatic light, which has only a single wavelength.

Explanation

Freons (CFCs) and halons are stable in the troposphere but break down under UV light in the stratosphere.

This breakdown releases chlorine and bromine, which destroy ozone molecules in the ozone layer.

Explanation

Fringing reefs are directly attached to a shoreline or lie close to the coast of volcanic islands.

They are the most common type of coral reef and develop in the shallow waters near land.

Explanation

Cardinal directions are the four main directions:

1. North
2. South
3. East
4. West

Northeast is an intercardinal (or ordinal) direction, not a cardinal one.