A diverging lens is used to permit clear vision of an object placed at infinity. The focal length of the lens is -100 cm.
<h3>What is focal length?</h3>
The focal length is half of the radius of curvature of the focal lens.
By the lens maker formula,
1/f = 1/v +1/u
where, v is the image distance and u is the object distance.
Give, the object is at infinity and the image must form at 100 cm, the the focal length will be
1/f = 1/ -100 + 1/∞
f = -100 cm
The focal length must be -100 cm for the diverging lens.
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Explanation:
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Answer:
301.48 J/s
Explanation:
We are given;
Temperature of the sky dropping to −40∘C: T_o = -40°C = -40 + 273 = 233 K
Temperature of your skin and clothes: T = 30°C = 30 + 273 = 303 K
Body surface area of human body is around 2 m². But here only half of the body is facing the sky, Thus Area is: A = 2/2 = 1 m²
To solve this, we will use the equation for thermal heat transfer known as the Stefan bolt Mann equation.
ΔQ/Δt = εσA(T⁴ - (T_o)⁴)
Where;
ΔQ/Δt is the rate at which you body loses energy by radiation
ε is the emissivity of the human body with a value of 0.97
σ is Stefan boltzmann constant with a value of 5.67 X 10^(-8) W/m².K⁴
Thus;
ΔQ/Δt = 0.97 × 5.67 X 10^(-8) × 1(303⁴ - 233⁴)
ΔQ/Δt = 301.48 J/s
