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4 years ago

How Many Days Would a Scientist Have To Wait For The Radioactivity To Be 12.5 The Starting Amount

Physics

2 answers:

irina1246 [14]4 years ago

5 0

They have to wait at least eight teen days

kiruha [24]4 years ago

3 0

They have to wait 18 days.

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A resistance is added in parallel to a 470 Ω resistance to give an effective resistance of 330 Ω. What is the approximate value

saw5 [17]

I think its c on the test I had

4 0

4 years ago

The objective lens of a certain refracting telescope has a diameter of 63.5 cm. The telescope is mounted in a satellite that orb

Ostrovityanka [42]

Answer:

0.255 m

Explanation:

We are given that

Diameter=d=63.5 cm= $63.5\times 10^{-2} m$

$1 cm=10^{-2} m$

L=265 km = $265\times 1000=265000 m$

Wavelength, $\lambda=500nm=500\times 10^{-9} m$

$1nm=10^{-9} m$

We have to find the minimum distance between two objects on the ground if their images are to be resolved by this lens.

$sin\theta=1.22\frac{\lambda}{d}$

$sin\theta=\frac{1.22\times 500\times 10^{-9}}{63.5\times 10^{-2}}$

$sin\theta=\approx \theta=9.606\times 10^{-7} rad$

$\frac{y}{L}=tan\theta\approx \theta$

$y=L\theta=265000\times 9.606\times 10^{-7}=0.255 m$

5 0

3 years ago

_____ electrons are the most important electrons to an atom .

nalin [4]

Answer:

stable is the answer

Explanation:

stable electrons

8 0

3 years ago

A car is traveling with constant velocity. this means that _______.

Lilit [14]

It is traveling in a straight line and its speed is not changing

7 0

3 years ago

One star has a temperature of 30,000 K and another star has a temperature of 6,000 K. Compared to the cooler star, how much more

Lilit [14]

Answer:

The hotter star radiates 625 times more energy per second from each square meter of its surface

Explanation:

Temperature of the hotter star is 30000 K

temperature of the cooler star = 6000 K

From Stefan-Boltzmann radiation laws, for a non black body

P = εσA $T^{4}$

where

P is the energy per second or power of radiation

ε is the emissivity of the body

σ is the Stefan-Boltzmann constant of proportionality

A is the area of the sun

T is the temperature of the sun

The sun can be approximated as a black body, and the equation reduces to

P = σA $T^{4}$

For the hotter body,

P = σA( $30000^{4}$ ) = 8.1 x 10^17σA J/s

For the cooler body,

P = σA( $6000^{4}$ ) = 1.296 x 10^15σA J/s

comparing the two stars energy

==> (8.1 x 10^17)/(1.296 x 10^15) = 625

This means that the hotter star radiates 625 times more energy per second from each square meter of its surface

5 0

3 years ago