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dolphi86 [110]
2 years ago
9

The average threshold of dark-adapted (scotopic) vision is 4.00 10-11 W/m2 at a central wavelength of 500 nm. If light with this

intensity and wavelength enters the eye and the pupil is open to its maximum diameter of 7.20 mm, how many photons per second enter the eye
Physics
1 answer:
Studentka2010 [4]2 years ago
8 0

Answer:

E = h f = h c / λ     energy of single photon

n E = 4.00E-11 W/m^2       energy required for visibility

n h c / λ = 4.00E-11          number of photons required for visibility (per square meter)

n = 4.00E-11 * 5.00E-7 / (6.63E-34 * 3.00E8)

n = 20.0E-18 / 19.9 E-26 = 1.00E8

100 million photons would be required on 1 m^2 to create visibility

a / A = π * (3.6E-3)^2 / 1 = 4.07E-5     fraction of area available

4.07E-5 * 1.00E8 = 4.07E3  photons required    

           

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Rain falling vertically will make vertical streaks on a car's side window. However,if the car is moving, the streaks are slanted
Alla [95]

When car is at rest the steaks makes makes vertical lines

which means the rain is falling in vertically downward direction

Now when car is moving with some speed v

Now the steaks makes and an angle 45 degree

So here we can say that relative velocity of rain with car is 45 degree

Now this is the resultant speed of rain in car frame

V_{rc} = V_r - V_c

now if relative velocity makes 45 degree angle so this vector must have same components in vertical and horizontal direction

Since we know that relative velocity is resultant of rain velocity and car velocity so we can say here its two components are rain velocity and car velocity

So these two components must be of same magnitude

as it makes 45 degree

because when two vector are of same magnitude then the resultant vector always makes 45 degree with them if these two vectors are perpendicular to each other

car is moving at same speed as the speed of rain

7 0
3 years ago
Describe how coal-fired power plant converts chemical energy in coal into electricity energy.
Ray Of Light [21]
Coal is burned and is used to boil water, which in turn produces steam. Now this steam is passed through nozzles. The steam turns a steam turbine. Now the turbine is coupled to a generator. Generator is an electro magnetic device used for conversion of mechanical energy into electrical energy. So in the generator a voltage difference is created and converted into electrical.


Hope this help : )
8 0
3 years ago
Read 2 more answers
A cube with sides of area 18 cm^2 contains a 6.0 nanoCoulomb charge. Find the flux of the electric field through the surface of
Vanyuwa [196]

Answer:

The flux of the electric field  is 677.6 Nm²/C

Explanation:

Given that,

Area = 18 cm²

Charge = 6.0 nC

We need to calculate the flux of the electric field

Using Gauss's law

\phi=\dfrac{q}{\epsilon_{0}}

Where, q = charge

\epsilon_{0} =permittivity of free space

Put the value into the formula

\phi=\dfrac{6.0\times10^{-9}}{8.854\times10^{-12}}

\phi=677.6\ Nm^2/C

Hence, The flux of the electric field  is 677.6 Nm²/C.

4 0
3 years ago
How many excess electrons must be distributed uniformly within the volume of an isolated plastic sphere 23.0 cm in diameter to p
lyudmila [28]

Answer:

10573375000

216.57162\ N/C

Explanation:

k = Coulomb constant = 8.99\times 10^{9}\ Nm^2/C^2

r = Distance = \dfrac{d}{2}=\dfrac{23}{2}=11.5\ cm

E = Electric field = 1150 N/C

Electric field is given by

E=\dfrac{kq}{r^2}\\\Rightarrow q=\dfrac{Er^2}{k}\\\Rightarrow q=\dfrac{1150\times 0.115^2}{8.99\times 10^9}\\\Rightarrow q=1.69174\times 10^{-9}\ C

Number of electrons is given by

n=\dfrac{1.69174\times 10^{-9}}{1.6\times 10^{-19}}\\\Rightarrow n=10573375000

Number of excess electrons is 10573375000

r = 0.115+0.15 = 0.265 m

E=\dfrac{kq}{r^2}\\\Rightarrow E=\dfrac{8.99\times 10^9\times 1.69174\times 10^{-9}}{0.265^2}\\\Rightarrow E=216.57162\ N/C

The electric field is 216.57162\ N/C

4 0
3 years ago
What kind of chemical reaction does the chemical equation sodium + chlorine sodium chloride represents
Pavlova-9 [17]
It represents combustion. 
5 0
3 years ago
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