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inna [77]
3 years ago
7

The human eye is a complex sensing device for visible light. The optic nerve needs a minimum of 2.0 × 10−17 J of energy to trigg

er a series of impulses that eventually reach the brain. How many photons of blue light (475 nm) are needed?

Chemistry
2 answers:
Karo-lina-s [1.5K]3 years ago
7 0
Number of photons can be calculated by dividing the needed energy by the energy per photon.

The minimum energy needed is given as 2 x 10^-17 joules
Energy per photon = hc / lambda where h is planck's constant, c is the speed of light and lambda is the wavelength
Energy per photon = (<span>6.626 x 10^-34 x 3 x 10^8) / (475 x 10^-9)
                              = 4.18 x 10^-19 J

number of photons = (2 x 10^-17) / (4.18 x 10^-19)
                               = 47.79 photons which is approximately 48 photons</span>
Sonja [21]3 years ago
5 0

The number of photons needed to get the energy to trigger a series of impulses that eventually reaches the brain is: 48.7 photons

<h3><em>Further explanation</em></h3>

The photoelectric effect is an electron coming out of a metal because of electromagnetic radiation

One type of electromagnetic radiation is light

Electrons can come out of metal because they absorb electromagnetic energy radiated on metals. There is also kinetic energy released from metal, which is according to the equation:

E = hf - hfo

fo = the threshold frequency of electromagnetic waves

Radiation energy is absorbed by photons

The energy in one photon can be formulated as

\large{\boxed{\bold{E\:=\:h\:.\:f}}}

Where

h = Planck's constant (6,626.10⁻³⁴ Js)

f = Frequency of electromagnetic waves

f = c / λ

c = speed of light

= 3.10⁸

λ = wavelength

Known wavelength 475 nm

475 nm = 475.10⁻⁹ m

We put it in the formula to find this light energy E = h. f

E = h. c /λ

E =: 6,626.10⁻³⁴. 3.10⁸ / 475 .10⁻⁹ m

E = 4.1.10⁻¹⁹

Because this is 1 photon energy, while the minimum energy required is 2.0 × 10⁻¹⁷ J, the number of photons needed is:

number of photons = 2.0 × 10−17 J: 4.1.10⁻¹⁹

number of photons = 48.7

<h3><em>Learn more</em></h3>

Electromagnetic radiation with wavelength of 745 nm

brainly.com/question/7590814

The energy of a photon

brainly.com/question/7353559

The equation E = hf

brainly.com/question/4177755

the approximate energy of a photon

brainly.com/question/7991589

The equation for photon energy

brainly.com/question/2741868

the wavelength of a photon whose energy is twice

brainly.com/question/6576580

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