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2 years ago

The sun radiates most strongly at a wavelength of about 550 nm. a star that radiated most strongly at 400 nm would be

1 answer:

5 0

550 nm is in the visible spectrum. 400 nm is in the ultra-violet spectrum. The shorter the wavelength, the bigger the energy of the light photon emitted. Therefore a star that emits 400 nm photons, is hotter than the Sun. A star that is hotter is either bigger than the Sun (and has about the same age), either younger than the Sun (and has about the same dimension).
Therefore a star that radiates at 400 nm would be hotter, bigger and younger than the Sun.

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A tennis player hits a ball 2.0 m above the ground. The ball leaves his racquet with a speed of 20 m/s at an angle 5.0 ∘ above t

ipn [44]

Answer:

ball clears the net

Explanation:

$v_{o}$ = initial speed of launch of the ball = 20 ms^{-1}

$\theta$ = angle of launch = 5 deg

Consider the motion of the ball along the horizontal direction

$v_{ox}$ = initial velocity = $v_{o} Cos\theta = 20 Cos5 = 19.92 ms^{-1}$

$t$ = time of travel

$X$ = horizontal displacement of the ball to reach the net = 7 m

Since there is no acceleration along the horizontal direction, we have

$X = v_{ox} t \\7 = v_{ox} t\\t = \frac{7}{v_{ox}}$ Eq-1

Consider the motion of the ball along the vertical direction

$v_{oy}$ = initial velocity = $v_{o} Sin\theta = 20 Sin5 = 1.74 ms^{-1}$

$t$ = time of travel

$Y_{o}$ = Initial position of the ball at the time of launch = 2 m

$Y$ = Final position of the ball at time "t"

$a_{y}$ = acceleration in down direction = - 9.8 ms⁻²

Along the vertical direction , position at any time is given as

$Y = Y_{o} + v_{oy} t + (0.5) a_{y} t^{2}\\Y = 2 + (20 Sin5) (\frac{7}{20 Cos5}) + (0.5) (- 9.8) (\frac{7}{20 Cos5})^{2}\\Y = 2.00758 m\\$

Since Y > 1 m

hence the ball clears the net

7 0

1 year ago

Given that an electric field of 3×106V/m3×106V/m is required to produce an electrical spark within a volume of air, estimate the

Andre45 [30]

Answer:

Length, l = 33.4 m

Explanation:

Given that,

Electrical field, $E=3\times 10^6\ V/m$

Let the electrical potential is, $V=10^8\ V$

We need to find the length of a thundercloud lightning bolt. The relation between electric field and the electric potential is given by :

$V=E\times d\\\\d=\dfrac{V}{E}\\\\d=\dfrac{10^8}{3\times 10^6}\\\\d=33.4\ m$

So, the length of a thundercloud lightning bolt is 33.4 meters. Hence, this is the required solution.

5 0

2 years ago

A light ray strikes a plane mirror at an angle of 23° to the normal. What is the angle between the reflected ray and the mirror?

tiny-mole [99]

Answer: $67^{\circ}$

Explanation:

Given

Ray of light incident on plane making an angle of $23^{\circ}$ with normal

Thus incident angle $i=23^{\circ}$

So according to the law of incidence is equal to angle of reflection

$\angle i=\angle r$

thus $\angle r=23^{\circ}$

and angle between mirror and reflected ray $=90^{\circ}-23^{\circ}$

$=67^{\circ}$

4 0

2 years ago

Which radioactive isotope would take the least amount of time to become stable? rubidium-91 iodine-131 cesium-135 uranium-238

Leno4ka [110]

The radioactive isotope that would take the least amount of time to become stable is rubidium-91. This is because this isotope is the most stable compared to the rest. This was determined by subtracting its atomic mass by its atomic number. The isotope with the least number of difference is the most stable, while the one with the greatest difference is the most unstable.

Difference:
Rubidium: 54 (most stable)
Iodine: 78
Cesium: 80
Uranium: 146 (least stable)

8 0

1 year ago

Read 2 more answers

What is the frequency of 20 mm microwaves? A) 100 MHz B) 400 MHz C) 15 GHz D) 73 GHz E) 98 GHz

Lera25 [3.4K]

Answer:

Explanation:

Given wavelength = 20 mm = 20 x 10⁻³ m

The microwaves are electromagnetic waves so their velocity will be equal to

3 x 10⁸ m /s.

Now frequency of microwave = velocity / wavelength

= 3 x 10⁸ / 20 x 10⁻³ = 1.5 x 10¹⁰ = 15 x 10⁹ = 15 GHz.

3 0

2 years ago