A student uses a Leslie's cube to investigate how different surfaces emit thermal radiation. The cube has four different vertical faces and is filled with boiling water so that all four surfaces are at the same temperature.
A radiation sensor is placed at a fixed distance from each surface to measure the quantity of emitted infrared radiation.
The four surfaces of the cube and four different sensor readings (in arbitrary units) are listed below. Surfaces:
Readings:
Match each surface to its correct sensor reading.
State what this experiment demonstrates about how the nature of a surface affects its ability to emit thermal radiation.
A differential thermometer consisting of a U-tube containing liquid of density 920 kg/m3920\text{ kg/m}^3920 kg/m3 is connected to two glass bulbs. One bulb is painted dull black and the other is painted shiny silver.
State the equation linking pressure difference, density, gravitational field strength (ggg), and height.
Calculate the pressure due to the liquid columns at point XXX when the height, hhh, of the column of liquid is 0.24 m0.24\text{ m}0.24 m. State the unit. (Take g=9.8 m/s2g = 9.8\text{ m/s}^2g=9.8 m/s2 or 10 m/s210\text{ m/s}^210 m/s2).
When the thermometer is placed near a hot radiant heater, the liquid level on the dull black side drops, whilst it rises on the shiny silver side. Explain these observations using your knowledge of heat transfer and particle theory.
Explain how the height difference, hhh, would change if a more dense liquid was used in the thermometer under the same conditions.
