The energy carried by the incident light is

where h is the Planck constant and f is the frequency of the light. The threshold frequency is the frequency that corresponds to the minimum energy needed to eject the electrons from the metal, so if we substitute the threshold frequency in the formula, we get the minimum energy the light must have to eject the electrons:
Answer:
Range of wavelength will be
to 
Explanation:
We have given range of frequency is 400-560 Hz
Speed of the light 
We have to find the range of the wavelength of signal transmitted
Ween know that velocity is given by
, here
is wavelength and f is frequency
So for 400 Hz frequency wavelength will be 
And wavelength for frequency 560 Hz 
So range of wavelength will be
to 
- (spring constant) (new length of spring - original length of spring) = Force applied to spring.
that is
-kx=F
Did you only have how far the cart traveled? No mass or acceleration or speed or time taken?
Answer:
A) Electrons only
Explanation:
In quantum mechanics, "electron cloud" refers to the region of space where electrons can be found in an atom. In fact, in quantum mechanics, it is not possible to predict the exact position of the electrons, so there is a region where electrons have a certain probability to be found.
Red is the lowest because it has the shortest wavelengths