Answer:
At the focus
Explanation:
In car head lights concave mirrors are used. The light bulbs in these headlights are place along the principal axis as shown in the figure. On this Principal axis light bulbs are place at the Focus to get maximum brightness. As from the figure we can conclude that light rays coming from infinity converse at focus thus, giving maximum brightness.
Answer:
If a material has high thermal conductivity, it is a conductor.
If a material has low thermal conductivity, it is an insulator.
The answer is
6.67 Ohms (I tried to find the ohms sign but it looks like the lululemon logo)
(a) 
The frequency of an electromagnetic wave is given by:

where
is the speed of the wave in a vacuum (speed of light)
is the wavelength
In this problem, we have laser light with wavelength
. Substituting into the formula, we find its frequency:

(b) 427.6 nm
The wavelength of an electromagnetic wave in a medium is given by:

where
is the original wavelength in a vacuum (approximately equal to that in air)
is the index of refraction of the medium
In this problem, we have

n = 1.48 (index of refraction of glass)
Substituting into the formula,

(c) 
The speed of an electromagnetic wave in a medium is

where c is the speed of light in a vacuum and n is the refractive index of the medium.
Since in this problem n=1.48, we find

Ultraviolet rays from the sun are very strong, therefore if direct contact is made with skin, it could cause sun burn, or in a worser case skin cancer