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2 years ago

How can we represent a narrow beam of light?

2 answers:

tatiyna2 years ago

8 0

Answer:It is easy to imagine representing a narrow beam of light by a collection of parallel arrows—a bundle of rays. As the beam of light moves from one medium to another, reflects off surfaces, disperses, or comes to a focus, the bundle of rays traces the beam's progress in a simple geometrical manner.

Explanation:

Yanka [14]2 years ago

7 0

Answer:

It is easy to imagine representing a narrow beam of light by a collection of parallel arrows—a bundle of rays. As the beam of light moves from one medium to another, reflects off surfaces, disperses, or comes to a focus, the bundle of rays traces the beam's progress in a simple geometrical manner.

I hope it's helpful!

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When an aluminum bar is connected between a hot reservoir at 720 K and a cold reservoir at 358 K, 3.00 kJ of energy is transferr

disa [49]

Answer:

a. -4.166 J/K

b. 8.37 J/K

c. 4.21 J/K

d. entropy always increases.

Explanation:

Given :

Temperature at hot reservoir , $T_h$ = 720 K

Temperature at cold reservoir , $T_c$ = 358 K

Transfer of heat, dQ = 3.00 kJ = 3000 J

(a). In the hot reservoir, the change of entropy is given by:

$dS_h= -\frac{dQ}{t_h}$ (the negative sign shows the loss of heat)

$dS_h= -\frac{3000}{720}$

= -4.166 J/K

(b) In the cold reservoir, the change of entropy is given by:

$dS_c= \frac{dQ}{t_c}$

$dS_c= \frac{3000}{358}$

= 8.37 J/K

(c). The entropy change in the universe is given by:

$dS=dS_h+dS_c$

= -4.16+8.37

= 4.21 J/K

(d). According to the concept of entropy, the entropy of the universe is always increasing and never decreasing for an irreversible process. If the entropy of universe decreases, it violates the laws of thermodynamics. Hence, in part (c), the result have to be positive.

5 0

3 years ago

Explain why the sound produced by every vibrating body cannot be heard by us ?

VMariaS [17]

Answer:

The human ear is not sensitive to every frequency of sound, rather, our hearing range is from 20Hz to 20,000Hz. This means sound frequencies outside this range are not audible to the human ear, which is why not every sound produced is heard. This is quite a blessing because if we could hear every vibrating body, then our ears would never stop listening: we won't be able to distinguish 'important sounds' from unimportant ones, rendering our ears effectively useless. Perhaps this is why we have a hearing range in the first place: sounds of our friends and our foes lie in 20Hz-20kHz range.

5 0

3 years ago

A kite is hovering over the ground at the end of a straight 38-m line. the tension in the line has a magnitude of 17 n. wind blo

postnew [5]

Let the tension in the thread will be at angle theta

now by force balance in x and y directions we can say

$17 cos\theta = 18 cos60$