The correct answer is
b. low frequencies and low energy.
In fact, microwaves and radio waves have frequency up to 
, which are really low compared, for instance, to the frequency of gamma rays (
). Moreover, the energy of an electromagnetic wave is directly proportional to its frequency:
where h is the Planck constant and f the frequency; therefore, low frequency means also low energy.
Answer:
velocity of mass when it slides of will be 1.36 m/sec
So option (b) will be correct option.
Explanation:
We have given mass of the slits m = 75 gram = 0.075 kg
Radius r = 75 cm = 0.75 m
Coefficient of kinetic friction 
Acceleration due to gravity 
When the mass slides of
So velocity of mass when it slides of will be 1.36 m/sec
So option (b) will be correct option.
Answer:
The type of light and the material of lenz.
Explanation:
1) As the investigation is based on how the thickness of a lens effect the other variable. Thickness of the lenz is independent variable. So Lidia has to experiment with the different thicknesses in order to find the effect on dependent variable.
2) As the investigation is based to find the point where the beam of light is focused. It's a dependent variable and Lidia has no control over it. So the only thing she can do is to measure and observe how it respond to the changes in independent variable.
3) For conclusion, she has to make sure that the other variables are not effecting the output or results that is the beam point where the light is focused. So she must have to kept constant the type of light and material of lenz otherwise she won't be able to discriminate the effect of thickness of lenz from other causes.
Answer:
P-waves travel through liquids and solid while S-waves only travel through solids.
Explanation:
Scientists are able to use the fact that P-waves travel through both solids and liquids and waves travel through only solids to determine what makes the different layers of the Earth.
