i think its iron...
<span>Presence of trace elements, irradiation and iron impurities give the gem its purplish color .
:))
merry christmas</span>
(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
Complete question is;
Jason works for a moving company. A 75 kg wooden crate is sitting on the wooden ramp of his truck; the ramp is angled at 11°.
What is the magnitude of the force, directed parallel to the ramp, that he needs to exert on the crate to get it to start moving UP the ramp?
Answer:
F = 501.5 N
Explanation:
We are given;
Mass of wooden crate; m = 75 kg
Angle of ramp; θ = 11°
Now, for the wooden crate to slide upwards, it means that the force of friction would be acting in an opposite to the slide along the inclined plane. Thus, the force will be given by;
F = mgsin θ + μmg cos θ
From online values, coefficient of friction between wooden surfaces is μ = 0.5
Thus;
F = (75 × 9.81 × sin 11) + (0.5 × 75 × 9.81 × cos 11)
F = 501.5 N
