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Andre45 [30]
3 years ago
15

Modern humans first appeared during the

Biology
2 answers:
stira [4]3 years ago
4 0
A. Most recent period of the Cenozoic era. 


ratelena [41]3 years ago
4 0

Answer:

The correct answer is A) most recent period of the Cenozoic era.

Explanation:

Modern humans belong to a species called Homo sapiens that first appeared approximately 200.000 years ago. The Cenozoic era is the latest, made of two periods (tertiary and quaternary) where the latest is the quaternary that goes from 1,8 to 0,01 million years.

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An owl has good night vision because its eyes can detect a light intensity as small as 5.0 × 10-13 W/m2. What is the minimum num
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Answer:

Thus, the minimum number of photons per second is 77.34

Explanation:

Light intensity, I_{min} =  5\times 10^{-13} W/m^{2}

Pupil has a diameter, d = 8.5 mm

                                      = 8.5 x 10^{-3} m

Radius of the eye, r = 4.25 x 10^{-3} m

∴ Area of the eye, A = \pi .r^{2}

                                 = 3.14\times \left ( 4.25\times 10^{-3} \right )^{2}

                                = 5.6\times 10^{-5} m^{2}

Let P_{min} be the minimum number of photons.

Therefore, P_{min} = I_{min} x A

                                              = 5\times 10^{-13} x 5.6\times 10^{-5}

                                             = 2.8\times 10^{-17} W

Thus the minimum number of photons is given by

N_{min}=P_{min}/E

where E = hc/\lambda

             = \left (6.63\times 10^{-34}\times 3\times 10^{8}  \right )/548\times 10^{-9}

            = 3.62\times 10^{-19} J

Therefore, N_{min} = \frac{2.8\times 10^{-17}}{3.62\times 10^{-19}}

                                              = 77.34 photons per second

Thus, the minimum number of photons per second is 77.34

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