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Nataly_w [17]
3 years ago
5

The visible spectrum of sunlight shows a range of colors from red to violet. This spectrum has numerous dark lines spread throug

hout it. Noting that the surface of the Sun is much cooler than the interior, so that the surface is comparable to a cool gas through which light passes, which of the following statements correctly explains the dark lines?
a. The cooler, denser surface material scatters certain wavelengths of light, forming dark lines.
b. The atoms at the surface absorb certain wavelengths of light, causing the dark lines at those wavelengths.
c. The atoms in the Sun’s interior emit light of specific wavelength, so that parts of the spectrum are dark.
d. The atoms at the surface are excited by the high interior temperatures, so that the dark lines are merely wavelengths at which those atoms don’t emit energy.
Physics
1 answer:
Alexeev081 [22]3 years ago
6 0
The correct answer is letter D
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The unit for work can be written as __________ or as the nickname ______
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N or joule cuz joule is newton’s
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3 years ago
Read 2 more answers
Please answer these: Q1. i. In what two ways combustion can be useful to us? Explain by giving examples. ii. Explain why decompo
kenny6666 [7]

Answer:

1) combustion can be used as a source of energy.

Combustion is used to power rockets

ii) Decomposition of sugar is a chemical change and new substances are formed.

2)corrosion of pipes

Corrosion of bridges

Corrosion of knives and blades at home

I) iron rusts due to the action of air and moisture bon the metal setting up an electrochemical process in which the iron is the anode. This leads to the corrosion of the iron metal.

ii) Rusting is a problem because it reduces the economic value of iron. Rust weakens iron and threatens the integrity of materials made from iron.

Iron rusting may lead to the collapse of a bridge

Iron rusting makes a blade blunt

Iron rusting weakens pipes made of iron

iii) Rusting of iron can be prevented by galvanizing the iron or by painting the iron.

3) chemical change leads to the formation of a new substance while physical change does not lead to the formation of a new substance.

Chemical changes are not easily reversible while physical changes are easily reversible.

ii)condensation of water vapour is a physical change

iii)

Electrolysis of water;

Two moles of water---> two moles of hydrogen gas + one mole of oxygen gas

Synthesis of water;

two moles of hydrogen gas + one mole of oxygen gas---->Two moles of water

Decomposition of sugar;

One mole of Sucrose---> twelve moles of carbon + eleven moles of water + heat

Six moles of carbon dioxide + six moles of water +energy------> one mole of sugar + six moles of oxygen

Explanation:

Combustion is useful as a source of energy because it is used in power generation. Currently, combustion is being used to power rockets. It is also used as a way of providing heat at home.

One of the characteristics of a chemical change is that it leads to the formation of new substances. Since the decomposition of sugar leads to the formation of carbon and water, it is an irreversible chemical change.

When water is heated, it is converted into vapour which can settle on a surface and convert back to liquid water. This is a physical change.

6 0
3 years ago
The Doppler effect using ultrasonic waves of frequency 2.25 × 106 Hz is used to monitor the heartbeat of a fetus. A (maximum) be
miss Akunina [59]

Answer:

v = 2.88 \times 10^7 m/s

Explanation:

As per Doppler's effect we know that the frequency of the sound that is observed by the detector is the reflected sound

This reflected sound is given as

f' = f (\frac{v - v_h}{v + v_h})

f' = 2.25\times 10^6(\frac{v - 1540}{v + 1540})

so we know that the beat frequency is

\Delta f = 240 Hz

so we will have

f - f' = \Delta f

2.25 \times 10^6 - 2.25\times 10^6(\frac{v - 1540}{v + 1540}) = 240

1 - (\frac{v - 1540}{v + 1540}) = 1.07 \times 10^{-4}

so we have

0.99989 = (\frac{v - 1540}{v + 1540})

1.99989\times 1540 = 1.067 \times 10^{-4} v

v = 2.88 \times 10^7 m/s

4 0
4 years ago
What is the purpose of control group ?
kirill [66]
Control group in a scientific experiment is a group separated from the rest of the experiment, it is where the independent variable being tested cannot influence the results. It isolates the independent variable's effects on the experiment and can helps rule out alternative explanations of the experimental results.
6 0
3 years ago
Cells are visualized using light microscopes and electron microscopes. Which statement about microscopes is false. Group of answ
denpristay [2]

Answer:

Light microscopes use light and glass objectives to illuminate and magnify objects

Explanation:

Light microscopes and electron microscopes are used to study cells. The electron microscope has many times more resolving power than the ordinary light microscope. A light microscope contains an objective lens and an eyepiece through which the final image is seen.

Both light and electron microscopes magnifies the image of the object. The magnifying power of an electron microscope is many times that of the light microscope.

4 0
3 years ago
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