A) 750 m
First of all, let's find the wavelength of the microwave. We have
is the frequency
is the speed of light
So the wavelength of the beam is
![\lambda=\frac{c}{f}=\frac{3\cdot 10^8 m/s}{12\cdot 10^9 Hz}=0.025 m](https://tex.z-dn.net/?f=%5Clambda%3D%5Cfrac%7Bc%7D%7Bf%7D%3D%5Cfrac%7B3%5Ccdot%2010%5E8%20m%2Fs%7D%7B12%5Ccdot%2010%5E9%20Hz%7D%3D0.025%20m)
Now we can use the formula of the single-slit diffraction to find the radius of aperture of the beam:
![y=\frac{m\lambda D}{a}](https://tex.z-dn.net/?f=y%3D%5Cfrac%7Bm%5Clambda%20D%7D%7Ba%7D)
where
m = 1 since we are interested only in the central fringe
D = 30 km = 30,000 m
a = 2.0 m is the aperture of the antenna (which corresponds to the width of the slit)
Substituting, we find
![y=\frac{(1)(0.025 m)(30000 m)}{2.0 m}=375 m](https://tex.z-dn.net/?f=y%3D%5Cfrac%7B%281%29%280.025%20m%29%2830000%20m%29%7D%7B2.0%20m%7D%3D375%20m)
and so, the diameter is
![d=2y = 750 m](https://tex.z-dn.net/?f=d%3D2y%20%3D%20750%20m)
B) 0.23 W/m^2
First we calculate the area of the surface of the microwave at a distance of 30 km. Since the diameter of the circle is 750 m, the radius is
![r=\frac{750 m}{2}=375 m](https://tex.z-dn.net/?f=r%3D%5Cfrac%7B750%20m%7D%7B2%7D%3D375%20m)
So the area is
![A=\pi r^2 = \pi (375 m)^2=4.42\cdot 10^5 m^2](https://tex.z-dn.net/?f=A%3D%5Cpi%20r%5E2%20%3D%20%5Cpi%20%28375%20m%29%5E2%3D4.42%5Ccdot%2010%5E5%20m%5E2)
And since the power is
![P=100 kW = 1\cdot 10^5 W](https://tex.z-dn.net/?f=P%3D100%20kW%20%3D%201%5Ccdot%2010%5E5%20W)
The average intensity is
![I=\frac{P}{A}=\frac{1\cdot 10^5 W}{4.42\cdot 10^5 m^2}=0.23 W/m^2](https://tex.z-dn.net/?f=I%3D%5Cfrac%7BP%7D%7BA%7D%3D%5Cfrac%7B1%5Ccdot%2010%5E5%20W%7D%7B4.42%5Ccdot%2010%5E5%20m%5E2%7D%3D0.23%20W%2Fm%5E2)
Answer:east
Explanation:Earth rotates or spins toward the east, and that's why the Sun, Moon, planets, and stars all rise in the east and make their way westward across the sky.
For a photographer that wishes to determine the color of light that he can use in a dark room that will not expose the films he is processing, having used a Blue Incandescent bulb, he should proceed to use a Red Incandescent bulb for the next trial.
The photographer in question is performing an experiment. For these kinds of experiments it is important to identify the variables present, which can be of three kinds:
- Control variables
- Dependent variables
- Independent variables
For this experiment, the dependent variable is the exposure of the light onto the films, given that this is what we wish to measure. The independent variable will be the color of the light being used which is what will affect the dependent variable.
The remaining variable must be the control variable. Unlike the previous variables, we can have more than one of these. The control variable is there to make sure that only the dependent variable is affecting the outcome. We do this by keeping the control variable the same through each trial, which is why the photographer should not change the type of bulb in the second experiment, changing only the color of the light.
To learn more visit:
brainly.com/question/1549017?referrer=searchResults
Answer : 12.7 cm = 127. mm
Answer:
The answer is 3213.6 grams.
Explanation:
In meters the room dimensions are 3.05-3.2-6.86.
Total volume of the room is:
![3.05*3.2*6.86=66.95](https://tex.z-dn.net/?f=3.05%2A3.2%2A6.86%3D66.95)
66.95 m3.
The density of carbon monoxide is 48 g/m3. Then total grams is present in a room measuring:
![66.95*48=3213.6](https://tex.z-dn.net/?f=66.95%2A48%3D3213.6)