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3 years ago

Lunar phases occur when the moon appears to change shape as seen from earth. What causes different phases of the moon?.

1 answer:

meriva3 years ago

8 0

Answer: The moon is said to be in full phase when the illuminated half of the moon is fully in position for us to see it. The "new moon" phase of the lunar cycle happens when the sun, moon, and earth are located in a straight line, with the moon between the earth and the sun. The moon is said to be in a "waxing" phase when it is moving from the new moon phase into the full moon phase. During this time, the amount of visible, illuminated moon will be gradually growing. The moon is said to be in a "waning" phase when it is moving from the full moon phase into the new moon phase. During this time, the visible portion of the moon will appear to be shrinking. A crescent moon occurs close to the new and full moon stages, whether the moon is waxing or waning. At this time, only a small sliver of the illuminated moon is visible to us.

Explanation:

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The following table lists the work functions of a few common metals, measured in electron volts. Metal Φ(eV) Cesium 1.9 Potassiu

Citrus2011 [14]

A. Lithium

The equation for the photoelectric effect is:

$E=\phi + K$

where

$E=\frac{hc}{\lambda}$ is the energy of the incident light, with h being the Planck constant, c being the speed of light, and $\lambda$ being the wavelength

$\phi$ is the work function of the metal (the minimum energy needed to extract one photoelectron from the surface of the metal)

K is the maximum kinetic energy of the photoelectron

In this problem, we have

$\lambda=190 nm=1.9\cdot 10^{-7}m$ , so the energy of the incident light is

$E=\frac{hc}{\lambda}=\frac{(6.63\cdot 10^{-34}Js)(3\cdot 10^8 m/s)}{1.9\cdot 10^{-7} m}=1.05\cdot 10^{-18}J$

Converting in electronvolts,

$E=\frac{1.05\cdot 10^{-18}J}{1.6\cdot 10^{-19} J/eV}=6.5 eV$

Since the electrons are emitted from the surface with a maximum kinetic energy of

K = 4.0 eV

The work function of this metal is

$\phi = E-K=6.5 eV-4.0 eV=2.5 eV$

So, the metal is Lithium.

B. cesium, potassium, sodium

The wavelength of green light is

$\lambda=510 nm=5.1\cdot 10^{-7} m$

So its energy is

$E=\frac{hc}{\lambda}=\frac{(6.63\cdot 10^{-34}Js)(3\cdot 10^8 m/s)}{5.1\cdot 10^{-7} m}=3.9\cdot 10^{-19}J$

Converting in electronvolts,

$E=\frac{3.9\cdot 10^{-19}J}{1.6\cdot 10^{-19} J/eV}=2.4 eV$

So, all the metals that have work function smaller than this value will be able to emit photoelectrons, so:

Cesium

Potassium

Sodium

C. 4.9 eV

In this case, we have

- Copper work function: $\phi = 4.5 eV$

- Maximum kinetic energy of the emitted electrons: K = 2.7 eV

So, the energy of the incident light is

$E=\phi+K=4.5 eV+2.7 eV=7.2 eV$

Then the copper is replaced with sodium, which has work function of

$\phi = 2.3 eV$

So, if the same light shine on sodium, then the maximum kinetic energy of the emitted electrons will be

$K=E-\phi = 7.2 eV-2.3 eV=4.9 eV$

7 0

4 years ago

Which is a unit of volume? A) centimeter B) meter C) milligram D) milliliter

german

Answer:

I think milligram is the correct answer.

6 0

4 years ago

Which process is a form of mechanical weathering?

marishachu [46]

Mechanical weathering is actually breaking down of rocks into smaller pieces by natural forces. Any weathering processes that can cause the physical breakdown of rocks without any type of change in the chemical composition of rocks, called mechanical weathering.

So, looking at each of the definitions in the options, we can easily choose:
1. Hydration : It's a process of absorbing water by substance.

2. Carbonation: It's a process of Carbon Dioxide dissolving in liquid (mostly water).

3. Oxidation : It's a process of oxygen reacting with some element.

4. Exfoliation: It's a process where the rocks erodes by peeling off in sheets or layer by layer rather than grain by grain.

As you can see the last one Exfoliation matches with the definition of mechanical weathering. It's one of its types.

8 0

4 years ago

Read 2 more answers

A MEMS-based accelerometer has a mass of m = 2 grams, an equivalent spring constant of k = 5 N/m, and an equivalent damping coef

pychu [463]

Answer:

The natural frequency = 50 rad/s = 7.96 Hz

Damping ratio = 0.5

Explanation:

The natural frequency is calculated in this manner

w = √(k/m)

k = spring constant = 5 N/m

m = mass = 2 g = 0.002 kg

w = √(5/0.002) = 50 rad/s

w = 2πf

50 = 2πf

f = 50/(2π) = 7.96 Hz

Damping ratio = c/[2√(mk)] = 0.1/(2 × √(5 × 0.002)) = 0.5

5 0

3 years ago

In the text "White House Press Release Announcing the Bombing of Hiroshima August 6, 1945" by President Truman, in which country

stepladder [879]

D
Japan is the answer

7 0

2 years ago