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3 years ago

14

Why do electromagnetic waves not require a medium for travel?

1 answer:

FinnZ [79.3K]3 years ago

8 0

Answer:

Because they propagate due to presence of magnetic and electric field.

Explanation:

An Electromagnetic wave is a transversal wave conformed of an electric field perpendicular to a magnetic field.

Maxwell established that an electric field can generate a magnetic field and vice versa, which allows the propagation of the electromagnetic wave without a medium.

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When an electron is displaced in a semiconductor, the hole that's left behind is

morpeh [17]

Answer:

A. attracted to the negative terminal of the voltage source.

Explanation:

When an electron is displaced in a semiconductor, the hole that's left behind is

A. attracted to the negative terminal of the voltage source.

The electron leaving leaves a net + charge, which is attracted to the negative terminal.

8 0

3 years ago

A bird sits on top of a 639 m tall tower. If it's gravitational potential energy up there is 2033 J, what is its mass?

iris [78.8K]

The mass of the bird is 0.32 kg.

<u>Explanation:</u>

Gravitational potential energy, the energy exhibited by an object at rest due to the influence of gravitational force. So the increase in distance of object from the surface of earth leads to increase in the gravitational potential energy. Thus,

$\text {Gravitational potential energy}=m \times \text { Acceleration } \times \text { Distance of bird from bottom }$

So, as the gravitational potential energy is given as 2033 J and the position of bird placed on the tall tower is 639 m away from the bottom, then the mass (m) of the bird can be found as below.

$m o f \text { bird }=\frac{\text {Gravitational potential energy}}{a \times \text {Distance}}=\frac{2033}{9.8 \times 639}=\frac{2033}{6262.2}$

So, finally we get the bird's mass as,

m of bird = 0.32 kg

7 0

3 years ago

A body travels 10 meters during the first 5 seconds of its travel, and it travels a total of 30 meters over the first 10 seconds

Nesterboy [21]

Answer:

c. 4 meters/second

Explanation:

The formula to calculate average speed is:

$s = \frac{x_{2} - x_{1} }{ t_{2} - t_{1} }$

7 0

3 years ago

An FM radio station broadcasts electromagnetic radiation at a frequency of 93.5 MHz. The wavelength of this radiation is _______

Alborosie

Answer:

3.21

Explanation:

The relation between frequency and wavelength is shown below as:

$c=frequency\times Wavelength
$

c is the speed of light having value $3\times 10^8\ m/s$

Given, Frequency = 93.5 MHz = $93.5\times 10^{6}\ Hz$

Thus, Wavelength is:

$Wavelength=\frac{c}{Frequency}$

$Wavelength=\frac{3\times 10^8}{93.5\times 10^{6}}\ m$

$Wavelength=3.21 \ m$

<u>Answer - A.</u>

7 0

3 years ago

A projectile is shot directly away from Earth's surface. Neglect the rotation of the Earth. What multiple of Earth's radius RE g

7nadin3 [17]

Answer:

(a) r = 1.062·R $_E$ = $\frac{531}{500} R_E$

(b) r = $\frac{33}{25} R_E$

(c) Zero

Explanation:

Here we have escape velocity v $_e$ given by

$v_e =\sqrt{\frac{2GM}{R_E} }$ and the maximum height given by

$\frac{1}{2} v^2-\frac{GM}{R_E} = -\frac{GM}{r}$

Therefore, when the initial speed is 0.241v $_e$ we have

v = $0.241\times \sqrt{\frac{2GM}{R_E} }$ so that;

v² = $0.058081\times {\frac{2GM}{R_E} }$

v² = ${\frac{0.116162\times GM}{R_E} }$

$\frac{1}{2} v^2-\frac{GM}{R_E} = -\frac{GM}{r}$ is then

$\frac{1}{2} {\frac{0.116162\times GM}{R_E} }-\frac{GM}{R_E} = -\frac{GM}{r}$

Which gives

$-\frac{0.941919}{R_E} = -\frac{1}{r}$ or

r = 1.062·R $_E$

(b) Here we have

$K_i = 0.241\times \frac{1}{2} \times m \times v_e^2 = 0.241\times \frac{1}{2} \times m \times \frac{2GM}{R_E} = \frac{0.241mGM}{R_E}$

Therefore we put $\frac{0.241GM}{R_E}$ in the maximum height equation to get

$\frac{0.241}{R_E} -\frac{1}{R_E} =-\frac{1}{r}$

From which we get

r = 1.32·R $_E$

(c) The we have the least initial mechanical energy, ME given by

ME = KE - PE

Where the KE = PE required to leave the earth we have

ME = KE - KE = 0

The least initial mechanical energy to leave the earth is zero.

3 0

3 years ago

Read 2 more answers