Answer:1. Transparent
2. Transparent
3. Opaque
Explanation: In a transparent medium light can pass through. For opaque objects it does not allow to pass through instead it is reflected back.
The correct answer is :
Unit vectors I and j along the x-axis and y-axis, respectively, define the Cartesian coordinate system. The radial unit vector r, which indicates the direction from the origin, and the unit vector t, which is orthogonal (perpendicular) to the radial direction, together create the polar coordinate system.
We can obtain the horizontal component by applying the trigonometric identity of Cos(Ф), and if we obtain the component on the x axle, such as 22000 (m)×Cos(51°) = x, we may determine that x = 13845.05 metres. We need to obtain the vector components because we already know the distance and the angle.
To learn more about Cartesian unit-vector refer the link:
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Answer:
f3 = 102 Hz
Explanation:
To find the frequency of the sound produced by the pipe you use the following formula:

n: number of the harmonic = 3
vs: speed of sound = 340 m/s
L: length of the pipe = 2.5 m
You replace the values of n, L and vs in order to calculate the frequency:

hence, the frequency of the third overtone is 102 Hz