Sediment discharge was historically approximately 270 million cubic meters/year of suspended load and 130 million cubic meters/year of bedload. This has decreased 80% since 1850 and can be divided into three periods: historical period (pre 1900), pre-dam period (1932-1952), and post dam (1963-1982). Suspended sediment loads declined 43% between the historical and pre-dam and 51% from pre-dam to post-dam periods. The size of sediment also decreased drastically including a 72% decrease in the sand fraction. Most of this is due to dams on the tributaries acting as sediment traps primarily for the coarser sediments. Large-scale land clearing for agriculture contributed to increased sediment loads in the historic period.

5 0

3 years ago

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

Lady bird [3.3K]

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

4 0

3 years ago

How does water and other molecules move across the membrane and in various solutions to maintain homeostasis

Kaylis [27]

Osmosis of Water Across the Membrane. Osmosis is the tendency for water molecules to move from where there is a higher concentration to where there is a lower one. ... The cell membrane helps to regulate and slow down the flow of water into the cell. This is yet another way that the cell membrane helps maintain homeostasis

3 0

3 years ago

Brown coat color in rabbits is dominant and white is recessive. Th allele for short fur is dominant, the allele for long fur is

Zarrin [17]

Yes because the dominant genes would cover up the recessive ones

4 0

3 years ago