# A2L Item 305

Goal: Unspecified.

Source: Unspecified.

Desert mirages are inverted images. From this, what can we conclude about the index of refraction of hot air compared to cold air?

1. nHOT AIR > nCOLD AIR
2. nHOT AIR + nCOLD AIR
3. nHOT AIR < nCOLD AIR
4. Mirages have nothing to do with refraction

None provided.

# A2L Item 111

Goal: Problem solving

Source: UMPERG-ctqpe182

What temperature reading (if any) would have the same numerical value on
both the Celcius and Fahrenheit temperature scales?

1. -40°
2. 180°
3. 72°
4. -25.6°
5. 568°
6. None of the above
7. Cannot be determined

### Commentary:

(2) This is a standard problem useful for determining whether students
are comfortable converting between the two temperature scales.

# A2L Item 090

Source: UMPERG

An ideal gas is allowed to expand slowly. The system is thermally
isolated.

Which statement regarding the final temperature is true?

1. T’ < T
2. T’ = T
3. T’ > T
4. Not enough information

### Commentary:

(1) For adiabatic expansion, TV(γ-1) is constant.
Since the volume increases, the temperature must decrease.

This result can be reasoned by considering the fact that work is done by
the gas. Since there is no heat transfer, the internal energy must
decrease. Since the internal energy of a perfect gas depends only upon
temperature, the temperature must decrease.

# A2L Item 091

Goal: Hone the concept of internal energy and heat.

Source: UMPERG-ctqpe180

Body A has a higher temperature than body B. Which of the following
statements is true?

1. Body A will feel hotter than body B.
2. Body A contains more energy than body B.
3. If placed in contact with each other, energy will flow from body A to
body B.
4. If placed in contact with a third body having temperature greater
than body A, body B will absorb more heat than A.
5. More than one statement is true.