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Anna007 [38]
2 years ago
10

Dinoflagellates are single-cell creatures that float in the world's oceans; many types are bioluminescent. When disturbed by mot

ion in the water, a typical bioluminescent dinoflagellate emits 100,000,000 photons in a 0.10s long flash of light of wavelength 460 nm .
What is the power of the Flash in watts?
Physics
1 answer:
arlik [135]2 years ago
3 0

Answer:

P = 43.2 10⁻¹⁰ W

Explanation:

To find the power, let's start by calculating the energy of each photon using the Planck equation

     E = h f

Where h is the Planck constant that is worth 6.63 10⁻³⁴ J s and f is the emitted frequency

The speed of light is related to wavelength and frequency

      c = lam f

Let's replace

    E = h c / lam

    E = 6.63 10⁻³⁴ 3. 10⁸/460 10⁻⁹

    E = 4.32 10⁻¹⁹ J

This is the energy of each photon emitted, the total energy is the product of this value by the number cded photons

Let's calculate the power

     P = W / t = Total E / t

     P= N E /t

    P = 1 10⁹ 4.32 10⁻¹⁹ / 0.10

    P = 43.2 10⁻¹⁰ W

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A solid cube of edge length r, a solid sphere of radius r, and a solid hemisphere of radius r, all made of the same material, ar
juin [17]

Answer:

Explanation:

The rate at which heat will be radiated is given by the expression

E = e Aσ ( T⁴ - T₀⁴ )

E is heat radiated , e is emissivity , A is area of surface , σ  is stephan's constant T is temperature of the object and T₀ is temperature of the surrounding .

For all the objects given , e , σ T and T₀ are same so E will solely dependent on area of the surface

surface area of cube= 6 r² ,

surface area of sphere = 4 π r²

= 12.56 r²

hemisphere = 2 π r²

= 6.28 r²

12.56 r² >6.28 r² > 6 r²

heat radiated by sphere > heat radiated by hemisphere > heat radiated by cube .

8 0
2 years ago
A11) A solenoid of length 18 cm consists of closely spaced coils of wire wrapped tightly around a wooden core. The magnetic fiel
vitfil [10]

Answer:

A

Explanation:

From a Solenoid we know that a magnetic fiel is always inversely proportional to lenght L or BL = constant

B= frac{\mu_0}{2R}

As I is constant

\frac{B2}{B1} = \frac{R1}{R2}

B2 = 2mT*\frac{18}{21}

B2 = 1.714mT

7 0
2 years ago
A wooden disk of mass m and radius r has a string of negligible mass is wrapped around it. If the disk is allowed to fall and th
Tju [1.3M]

Answer:

a = \frac{2}{3}g

T = \frac{mg}{3}

Explanation:

As the disc is unrolling from the thread then at any moment of the time

We have force equation as

mg - T = ma

also by torque equation we can say

TR = I\alpha

TR = \frac{1}{2}mR^2(\frac{a}{R})

T = \frac{1}{2}ma

Now we have

mg - \frac{1}{2}ma = ma

mg = \frac{3}{2}ma

a = \frac{2}{3}g

Also from above equation the tension force in the string is

T = \frac{1}{2}ma

T = \frac{mg}{3}

7 0
2 years ago
A boy on a bicycle approaches a brick wall as he sounds his horn at a frequency 400 hz. the sound he hears reflected back from t
Mashutka [201]
As the question is about changing in frequency of a wave for an observer who is moving relative to the wave source, the concept that should come to our minds is "Doppler's effect."

Now the general formula of the Doppler's effect is:
f = (\frac{g + v_{r}}{g + v_{s}})f_{o} -- (A)

Note: We do not need to worry about the signs, as everything is moving towards each other. If something/somebody were moving away, we would have the negative sign. However, in this problem it is not the issue.

Where,
g = Speed of sound = 340m/s.
v_{r} = Velocity of the receiver/observer relative to the medium = ?.
v_{s} = Velocity of the source with respect to medium = 0 m/s.
f_{o} =  Frequency emitted from source = 400 Hz.
f = Observed frequency = 408Hz.

Plug-in the above values in the equation (A), you would get:

408 = ( \frac{340 + v_{r}}{340 + 0})*400

\frac{408}{400} =  \frac{340 + v_{r}}{340}

Solving above would give you,
v_{r} = 6.8 m/s

The correct answer = 6.8m/s



7 0
2 years ago
A 10-kilogram box is at static equilibrium, and the downward pull of gravity acting on the box is 98 newtons. What is the minimu
Nikolay [14]
The box is at equilibrium, so the net force on the box is zero (the force of gravity on the box is equal to the force exerted up on the box by the surface on which it rests.)
To pick up the box, our upward force must be greater than the force of gravity on the box (the weight). So, we must lift up the box with a force greater than 98 newtons. :)
4 0
2 years ago
Read 2 more answers
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