2. A magnifying glass is an example of a _ lens.A. converging
B. double-concave
C. plano-convex
D. plano-concave
Student Answer: C
Answer: Incorrect
Reference:

3. If the distance from a converging lens to the object is less than the focal length of the lens, the image will be _ the object.
A. real, inverted, and smaller than
B. virtual, upright, and larger than
C. virtual, upright, and smaller than
D. real, inverted, and larger than
Student Answer: A
Answer: Incorrect
Reference:

4. Which of the following values represents an index of refraction of an actual material?
A. .25
B. 0
C. .5
D. 1.25
Student Answer: C
Answer: Incorrect
Reference:

5. Which, if any, of these mirrors can produce a real image?
A. Plane
B. Convex spherical
C. No mirrors can produce a real image.
D. Concave spherical
Student Answer: A
Answer: Incorrect
Reference:

6. When white light is incident on a prism, which one of the resulting color components will have the lowest index of refraction?
A. Yellow
B. Blue
C. Green
D. Orange
Student Answer: C
Answer: Incorrect
Reference:

12. Which of the following is not a reason fluorescent lamps are advantageous over incandescent lamps?
A. Fluorescent lamps operate at a higher temperature than incandescent lamps.
B. Fluorescent lamps are more efficient than incandescent lamps.
C. Fluorescent lamps dissipate more energy as light instead of heat than incandescent lamps.
D. Fluorescent lamps produce light with less glare than incandescent lamps.
Student Answer: B
Answer: Incorrect
Reference:

15. Which of the following is not a characteristic of electromagnetic waves?
A. They can travel through a vacuum.
B. They can be refracted.
C. They can be reflected.
D. They can travel at various speeds through any one material.
Student Answer: B
Answer: Incorrect
Reference:

16. A ray at which angle would produce the most glare?
A. 37 degrees
B. 70 degrees
C. 25 degrees
D. 59 degrees
Student Answer: B
Answer: Incorrect
Reference:

18. Which of the following statements is true of glare control?
A. Using bulbs that aren't frosted will help to diffuse the light and reduce glare.
B. Special care must be taken to prevent glare where a low illuminance is required.
C. Redirecting lamp fixtures and adjusting bulb types will do little to control glare.
D. Indirect lighting is preferred to direct lighting because it produces less glare.
Student Answer: C
Answer: Incorrect
Reference:

19. Which of the following objects uses two converging lenses to produce two images, the second of which is virtual, magnified, and inverted?
A. Slide projector
B. Compound microscope
C. Corrective eyeglasses
D. Camera
Student Answer: D
Answer: Incorrect
Reference:

20. The light intensity of a source is 100 candelas. The illuminance on a surface is 4 lux. How far is the surface from the source?
A. 4 meters
B. 6 meters
C. 5 meters
D. 7 meters
Student Answer: B
Answer: Incorrect

Answers

Answer 1

Answer: The answer to question 2 is C. A magnifying glass is an example of a plano-convex lens, where one side of the lens is flat and the other is a convex curve. The answer to question 3 is either B or C. A converging lens is curved on both sides and so the rays of light coming out of it converge at a point, which is known as the focal point. When the object is inside the focal point, the image is real and inverted. If it is inside the focal point, the image is virtual and upright. Therefore the image in this question will be upright. The focal length is the distance between the image that is being magnified and the centre of the magnifying lens. A real image can only be formed when the object is further away from the lens than the focal length. Therefore, in this question, the image is virtual, as the object is closer to the lens than the focal length. The answer to question 4 is D because the index of refraction cannot be less than 1. The answer to question 5 is D because only concave mirrors can produce real images; other types produce virtual images. For question 6, the answer is D. In the rainbow, each of the colours refracts at a slightly different angle; red has the smallest refractive index and violet the largest. Of the options, orange is closest to red. For question 12, A is the answer. A higher operating temperature is not a reason fluorescent lamps are better than incandescent lamps because they have a lower operating temperature. Question 15: all of these are characteristics of different electromagetic waves. For question 18, B is true - special care must be taken when low illuminance is required to reduce glare. The answer to question 19 is B - a compound microscope makes use of two lenses. For question 20, the answer is 5 meters away. The illuminance (E) is equal to light intensity (I) divided by the square distance from the light source (d). Therefore, 4 = 100/d squared. To switch this around, d squared is equal to 100/4 = 25. Then find the square root of 25, which is 5.

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How many moles are in 987 grams of Ra(OH)2?

Answers

The number of moles in 987 grams of Ra(OH)2 = 3.8 moles

Calculating number of moles

Ra = 226g

O= 16g

H = 1

Therefore molar mass of Ra(OH)2= 226+ (16+1)×2

= 260g/mol

The molar mass of Ra(OH)2 = 260g/mol

Thus means that 260g of Ra(OH)2 makes up 1 mole

Therefore, 987 g = X moles

Make X moles the subject of formula,

X mole = 987/260

= 3.8 moles

Therefore, the number of moles in 987 grams of Ra(OH)2 = 3.8 moles

Learn more about molar mass here:

brainly.com/question/14469428

Answer : 3.79 moles are in 987 grams of $Ra(OH)_2$ .

Solution : Given,

Mass of $Ra(OH)_2$ = 987 g

Molar mass of $Ra(OH)_2$ = 260 g/mole

Now we have to calculate the moles of $Ra(OH)_2$ .

Formula used :

$\text{Moles of }Ra(OH)_2=\frac{\text{Mass of }Ra(OH)_2}{\text{Molar mass of }Ra(OH)_2}$

Now put all the given values in this formula, we get the moles.

$\text{Moles of }Ra(OH)_2=(987g)/(260g/mole)=3.79moles$

Therefore, 3.79 moles are in 987 grams of $Ra(OH)_2$ .

Which of the following statements about ice melting is true?a. Water molecules move into a fixed position.
b. Energy flows from the surroundings to the ice.
c. Water molecules lose energy.
d. The temperature of the ice increases as it melts

Answers

The statement about ice melting that is true is that the temperature of the ice increases as it melts. The answer is letter D. The rest of the choices do not answer the question above.

The sign of ΔHrxn and ΔSrxn for several different reactions are given.In which case is the reaction spontaneous at all temperatures?
ΔHrxn<0; ΔSrxn>0ΔHrxn<0; ΔSrxn<0ΔHrxn>0; ΔSrxn<0ΔHrxn>0; ΔSrxn>0

Answers

The answer is ΔSrxn>0 and ΔHrxn<0

This is because of the thermodynamic equation of the Gibbs Free Energy given by:

ΔG = ΔH – TΔS

First, it is important to note that spontaneous reactions are usually given by ΔG <0, ΔH<0 and ΔS>0. However, ΔG is the most important identifier of a thermodynamic process, so it is best to figure out the conditions that would give a negative ΔG.

For the equation's first term (ΔH), ΔG decreases when ΔH is decreased. For the second term TΔS, it can be observed that ΔG decreases when TΔS is increased due to the negative or minus sign.

So for all temperatures, ΔG is kept negative if ΔH is negative and TΔS is positive (because of the negative sign).

Would the following errors increase, decrease, or have no effect on the calculated moles of gas collected in the experiment? Explain your answers in complete sentences.a) The measured mass of the magnesium was smaller than the true mass.
b) The actual temperature of the hydrogen gas is less than room temperature.

Answers

a. If the actual mass of Magnesium used was larger then the measured and the amount of gas produced should be greater
b. when gas was cooler than its surroundings its density would be greater and the volume would appear to be smaller. This is because the gas molecules are very active and when heated they will expand.
so they both bound increase the calculated moles of gas collected in the experiment

Which change occurs when an atom in an excitedstate returns to the ground state?
(1) Energy is emitted.
(2) Energy is absorbed.
(3) The number of electrons decreases.
(4) The number of electrons increases.

Answers

Answer: The correct option is (1).

Explanation:

Whenever an atom in an excited state returns back to its ground state the energy is emitted out in the form of the radiation and the value of energy emitted can be determined by using the expression:

$E=(hc)/(\lambda )$

Where E = Energy of the radiation in joules

h = Planck's constant = $6.63* 10^(-34) J.s$

$\lambda$ = Wavelength of the radiation in meters.

The change that occurs when an atom in an excited state returns to the ground state is that (1) energy is emitted.
It is emitted by photons in the form of light, or in some cases, heat.

The time required for one-half of the atoms from a sample of a radioactive substance to decay is called its _____.a. half-life
b. beta decay
c. alpha decay
d. isotope number

Answers

The half life, this is how long it takes for half of the atoms to decay

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Which statement describes an intensive property of matter?A. It is the same for every sample of a single substance. B. It depends on how a substance was formed. C. It is the same for every sample of every substance. D. It depends on the amount of substance present.