Physics, 05.04.2020 12:54 izzyisawesome5232

A hydrogen line in a star's spectrum has a frequency of 4.57x10^14 Hz when stationary. In Altair's spectrum, it is shifted upward by 3.98x10^10 Hz. What is Altair's velocity relative to us? (Unit=m/s)

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Answer from: andrealeon2000

26125 m/s

Explanation:

The Doppler effect occurs when there is a source of a wave in relative motion with respect to an observer. In this situation, the frequency of the wave observed by the observer appears to be shifter with respect to the real frquency. In particular:

- If the source of the wave is moving away from the observer, there is an appareant decrease in frequency

- If the source of the wave is moving towards the observer, there is an apparent increase in frequency

This phenomenon occurs with any type of waves, also with light waves.

For light waves, the apparent frequency of the light emitted by the source is given by:

$f'=\frac{c}{c\pm v}f$

where

f' is the observed frequency

f is the real frequency

$c=3.0\cdot 10^8 m/s$ is the speed of light in a vacuum

is the velocity of the source, which is positive if the source is moving away, negative if the source is moving towards the observer

Here we have:

$f=4.57\cdot 10^{14}Hz$ is the real frequency of the hydrogen line

$f'=f+3.98\cdot 10^{10}=4.570398\cdot 10^{14} Hz$ is the observed frequency

The observed frequency is higher than the real frequency, so the star is moving towards us; so the equation will have a negative sign for the velocity:

$f'=\frac{c}{c-v}f$

Where here v is the velocity of the star. Solving for v, we find:

$c-v=c\frac{f}{f'}\\v=c(1-\frac{f}{f'})=(3.0\cdot 10^8 )(1-\frac{4.57\cdot 10^{14}}{4.570398\cdot 10^{14}})=26125 m/s$

Answer from: Quest

answer: the correct answer is 1.

explanation: there are various process in which a radioactive nuclei decays:

1) alpha decay: in this process, a heavier nuclei decays into lighter nuclei by releasing alpha particle. the mass number is reduced by 4 units.

$_a^z\textrm{x}\rightarrow _{a-2}^{z-4}+_2^4\alpha$

2) electron capture: in this decay process, a parent nuclei absorbs an electron and gets converted into a neutron. simply, a proton and an electron combines together to form a neutron. mass number does not change in this process.

$_a^z\textrm{x}+_{-1}^0\textrm{e}\rightarrow _{z-1}^a\textrm{y}$

3) gamma ray emission: it is a decay process in which an unstable nuclei gives excess energy by a spontaneous electromagnetic process. this decay releases $\gamma -radiations$ . this process does not change the mass number.

$_a^z\textrm{x}^*\rightarrow _a^z\textrm{x}+_0^0\gamma$

4) positron emission: it is a type of decay process, in which a proton gets converted to neutron and an electron neutrino. this is also known as $\beta ^+$ -decay. in this the mass number remains same.

$_a^z\textrm{x}\rightarrow _{z-1}^a\textrm{y}+_{+1}^0e$

from the above information, we see that only alpha-decay is producing a change in the mass number of the nucleus.

Answer from: Quest

ι вєℓιєνє ιт ιѕ тнє fιяѕт ¢нσι¢є(α.)

нє ѕнσυℓ∂ ѕмιℓє ρσℓιтℓу αи∂ ѕρєαк тσ тнє ρєяѕσи ωнσ ιѕ ιитєяяυριиg αfтєя тнє ∂ιѕ¢υѕѕισи

нσρє ι ¢συℓ∂ нєℓρ.

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A hydrogen line in a star's spectrum has a frequency of 4.57x10^14 Hz when stationary. In Altair's s...

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