To determine which equation Albert Einstein used to explain the photoelectric effect, we need to identify the correct relationship between energy (E), Planck's constant (h), and frequency (v).
Einstein's photoelectric equation is given by:
[tex]\[ E = h \times v \][/tex]
Now let's examine each of the provided options:
1. [tex]\( E = \frac{h}{v} \)[/tex]
- This option suggests that energy is equal to Planck's constant divided by the frequency. This is incorrect according to Einstein's equation.
2. [tex]\( E = h w \)[/tex]
- This option suggests that energy is proportional to Planck's constant and another term (w). Since it's possible there might be a typo and 'w' should actually be 'v', this could be the correct relationship.
3. [tex]\( E = \frac{\nu}{h} \)[/tex]
- This option suggests that energy is equal to the frequency divided by Planck's constant, which is incorrect.
4. [tex]\( E = h - v \)[/tex]
- This option suggests that energy is equal to Planck's constant minus the frequency, which is also incorrect.
Given these options, the correct one that aligns with Einstein's photoelectric equation, assuming that there was a typo and 'w' was intended to be 'v', is:
[tex]\[ \boxed{2} \][/tex]
So, the equation [tex]\( E = hw \)[/tex] (assuming 'w' is a typo for 'v') was used by Albert Einstein to explain the photoelectric effect.
