Which of these is not an example of work? A. Lifting a bag B. Holding a heavy weight C. Pushing a door open D. Kicking a ball
1 answer:
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Answer:
1341.03 V/m
Explanation:
The power output per unit area is the intensity and also the is the magnitude of the Poynting vector.
= cε₀
⇒ = cε₀
Where;
P is the power output
A is the area of the beam
c is speed of light
ε₀ is permittivity of free space 8.85 × 10⁻¹² F/m
is the average (rms) value of electric field
Making electricfield the subject of the equation
= P / Acε₀
= √(P / Acε₀)
But area A = πr²
= √(P / πr²cε₀)
Given:
Output power, P = 15 mW = 0. 015 W
Diameter, d = 2 mm = 0.002 m
⇒ Radius,
Solving for average (rms) value of electric field;
= 1341.03 V/m
The question is missing a diagram of the ray reflection. I attached a diagram which comes from a similar question in the answer section. The full question should be as follows:
Two plane mirrors intersect at right angles. A laser beam strikes the first of them at a point d = 10.0cmfrom their point of intersection, as shown in the figure. For what angle of incidence at the first mirror will this ray strike the midpoint of the second mirror (which is s=29.0cm long) after reflecting from the first mirror?
Answer:
34.6°
Explanation:
To strike the midpoint of the second mirror, the ray light will have to travel half of the distance vertically
i.e. 29/2 = 14.5
We can solve this through trigonometry.
Let the angle between the ray and the vertical plane mirror is known as α
tan α = 10/14.5
α = = 34.6°
The angle of incidence is the angle between the ray and the normal line of the mirror.
Let angle of incidence of first mirror be β
β = α = 34.6
