Explanation:
Given that,
Initial speed of the rock, u = 30 m/s
The acceleration due to gravity at the surface of the moon is 1.62 m/s².
We need to find the time when the rock is ascending at a height of 180 m.
The rock is projected from the surface of the moon. The equation of motion in this case is given by :

It is a quadratic equation, after solving whose solution is given by:
t = 7.53 s
or
t = 8 seconds
(e)If it is decending, v = -20 m/s
Now t' is the time of descending. So,

Let h' is the height of the rock at this time. So,

or
h' = 155 m
Answer:
The maximum wavelength is 492 nm.
Explanation:
Given that,
Angular separation 
Suppose a telescope with a small circular aperture of diameter 2.0 cm.
We need to calculate the maximum wavelength
Using formula of angular separation


Put the value into the formula

For small angle 



Hence, The maximum wavelength is 492 nm.
Answer:
On the wavelength
Explanation:
Visible light is just a small portion of the electromagnetic spectrum, which classifies all the electromagnetic waves from shortest wavelength (gamma rays) to longest wavelength (radio waves).
Visible light refers to the part of the spectrum which has wavelength between 380 nm and 750 nm. These are the only electromagnetic wave that our eyes can see, and depending on their wavelength, they appear as a different color. In particular, each color corresponds to a different range of wavelengths:
Violet: 380-450 nm
Blue: 450-495 nm
Green: 495-570 nm
Yellow: 570-590 nm
Orange: 590-620 nm
Red: 620-750 nm
charged objects will either attract or repel other charged objects