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ipn [44]
3 years ago
15

Recall from Chapter 1 that a watt is a unit of en- ergy per unit time, and one watt (W) is equal to one joule per second ( J·s–1

). A 100-W incandescent light- bulb produces about 4% of its energy as visible light. Assuming that the light has an average wavelength of 510 nm, calculate how many such photons are emit- ted per second by a 100-W incandescent lightbulb.
Physics
1 answer:
harkovskaia [24]3 years ago
3 0

Answer:

Explanation:

The energy of a photon is given by the equation E_p=h f, where h is the <em>Planck constant</em> and f the frequency of the photon. Thus, N photons of frequency f will give an energy of E_N=N h f.

We also know that frequency and wavelength are related by f=\frac{c}{\lambda}, so we have E_N=\frac{N h c}{\lambda}, where c is the <em>speed of light</em>.

We will want the number of photons, so we can write

N=\frac{\lambda E_N}{h c}

We need to know then how much energy do we have to calculate N. The equation of power is P=E/t, so for the power we have and considering 1 second we can calculate the total energy, and then only consider the 4% of it which will produce light, or better said, the N photons, which means it will be E_N.

Putting this paragraph in equations:

E_N=(\frac{4}{100})E=0.04Pt=(0.04)(100W)(1s)=4J.

And then we can substitute everything in our equation for number of photons, in S.I. and getting the values of constants from tables:

N=\frac{\lambda E_N}{h c}=\frac{(520 \times10^{-9}m) (4J)}{(6.626\times10^{-34}Js) (299792458m/s)}=1.047 \times10^{19}

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A jogger accelerates from rest to 4.86 m/s in 2.43 s. A car accelerates from 20.6 to 32.7 m/s also in 2.43 s. (a) Find the magni
Aleonysh [2.5K]

Explanation:

It is given that,

Initially, the jogger is at rest u₁ = 0

He accelerates from rest to 4.86 m, v₁ = 4.86 m

Time, t₁ = 2.43 s

A car accelerates from u₂ = 20.6 to v₂ = 32.7 m/s in t₂ = 2.43 s

(a) Acceleration of the jogger :

a=\dfrac{v-u}{t}

a=\dfrac{4.86\ m/s-0}{2.43\ s}

a₁ = 2 m/s²

(b) Acceleration of the car,

a=\dfrac{v-u}{t}

a=\dfrac{32.7\ m/s-20.6\ m/s}{2.43\ s}

a₂ = 4.97 m/s²

(c) Distance covered by the car,

d_1=u_1t_1+\dfrac{1}{2}a_1t_1^2

d_1=0+\dfrac{1}{2}\times 2\times (2.43)^2

d₁ = 5.904 m

Distance covered by the jogger,

d_2=u_2t_2+\dfrac{1}{2}a_2t_2^2

d_2=20.6\times 2.43+\dfrac{1}{2}\times 4.97\times (2.43)^2

d₂ = 64.73 m

The car further travel a distance of, d = 64.73 m - 5.904 m = 58.826 m

Hence, this is the required solution.

5 0
2 years ago
What must be true about a surface in order for diffuse reflection to occur?
balu736 [363]

Answer:

carpet

Explanation:

Diffuse reflection is the reflection of light from a surface such that an incident ray is reflected at many angles rather than at just one angle as in the case of specular reflection.

The structure of carpet's surface is as shown. Thus it shows large amount of diffuse reflection.

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3 years ago
Which force is greater the earth’s pull on the moon or the moon’s pull on the earth
Vitek1552 [10]

Answer:

The earth's pull on the moon

Explanation:

Earth exerts a gravitational pull on the moon 80 times stronger than the moon's pull on the Earth.

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3 years ago
What is the name of the ratio of the voltage applied to a circuit and the current in a circuit
malfutka [58]
Resistance is the name of the ratio of the voltage applied to a circuit and the current in a circuit. Goes under <span>Ohm's Law</span>
4 0
3 years ago
If we want to describe work, we must have
tresset_1 [31]

The answer is C

Hope that helps!

Good luck :)

8 0
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