Physics Concepts in Wave and Radiation

The background count is measured by placing the detector in a location without any radioactive sources present. This count represents the natural radiation level in the environment.

The count rate decreases as the radioactive nuclei decay over time. The number of unstable nuclei that can decay decreases exponentially, leading to a lower count rate.

The half-life is the time it takes for the count rate to decrease to half of its initial value. This can be determined by finding the time it takes for the count rate to halve on the decay curve.

<p>A longer half-life indicates a more stable nucleus. Nuclei with shorter half-lives decay more rapidly.</p> Signup and view all the answers

<p>Sound waves can diffract around obstacles, allowing them to bend and travel around corners. This phenomenon allows the student to hear the siren even when the fire engine is not visible.</p> Signup and view all the answers

<p>0.2 Hz</p> Signup and view all the answers

<p>Wave speed is equal to frequency multiplied by wavelength.</p> Signup and view all the answers

<p>Speed = Frequency x Wavelength. The units for frequency are Hz (Hertz), the units for wavelength are meters (m), and the units for speed are m/s (meters per second).</p> Signup and view all the answers

<p>2.4 m/s</p> Signup and view all the answers

<p>The normal is a line perpendicular to the surface of the water at the point where the light ray enters the water. It helps determine the angles of incidence and refraction.</p> Signup and view all the answers

<p>The speed of light increases as it travels from water to air.</p> Signup and view all the answers

<p>The light ray will bend away from the normal.</p> Signup and view all the answers

<p>Refraction is the bending of light as it passes from one medium to another. In this case, the light ray from the fish is refracted as it enters the air, making the fish appear to be in a different location than its actual position.</p> Signup and view all the answers

<p>Because of refraction, the light rays from the fish bend as they enter the air, causing the fish to appear higher than it actually is.</p> Signup and view all the answers

<p>No, the diagram would be reversed, showing the laser beam entering the water and bending towards the normal.</p> Signup and view all the answers

<p>The thermistor decreases its resistance when the temperature falls, allowing current to flow and activating the relay, thus switching on the heater.</p> Signup and view all the answers

<p>The relay acts as a switch that is operated by the current from the thermistor, turning the heater on when sufficient current flows.</p> Signup and view all the answers

<p>Increasing the resistance of R raises the threshold temperature for switching on the heater, meaning it will turn on at a higher temperature.</p> Signup and view all the answers

<p>If the thermistor fails in a low-resistance state, the heater may remain on continuously, potentially causing overheating.</p> Signup and view all the answers

<p>In a thermistor, resistance decreases as temperature increases, which allows more current to flow through the circuit.</p> Signup and view all the answers

<p>Altering the supply voltage can change the current flowing through the circuit, potentially affecting the relay's operation and heater performance.</p> Signup and view all the answers

<p>Safety features should include a fuse or circuit breaker to prevent overheating and an over-temperature cutoff to shut off the heater.</p> Signup and view all the answers

<p>The relationship indicates that the ratios of resistances are equal to the ratios of voltages in a circuit.</p> Signup and view all the answers

<p>R1 = 700 Ω.</p> Signup and view all the answers

<p>It implies that the equivalent resistance seen from the terminals is 700 Ω.</p> Signup and view all the answers

<p>As Rth increases, Vth also increases.</p> Signup and view all the answers

<p>When Vth reaches 2·0 V, the MOSFET or transistor turns on.</p> Signup and view all the answers

<p>The relay switches on the heater when the MOSFET activates.</p> Signup and view all the answers

<p>The switching voltage determines when the MOSFET activates, controlling power delivery.</p> Signup and view all the answers

<p>The voltage across the thermistor affects the turn-on state of the MOSFET/transistor.</p> Signup and view all the answers

<p>Monitoring Rth is important because it directly impacts the voltage and functionality of the circuit.</p> Signup and view all the answers

<p>A half box tolerance indicates the acceptable range of error in measurements.</p> Signup and view all the answers

<p>Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points. It is expressed as $V = IR$ where $V$ is voltage, $I$ is current, and $R$ is resistance.</p> Signup and view all the answers

<p>To calculate the current $I$, use the formula $I = rac{V}{R}$ by substituting the given voltage and resistance values.</p> Signup and view all the answers

<p>Using the values, $I = rac{3.0 V}{700 Ω} = 0.00429 A$ or approximately $4.29 mA$.</p> Signup and view all the answers

<p>Significant figures are important in providing accuracy in measurements and calculations; they ensure that reported values reflect the precision of the initial data.</p> Signup and view all the answers

<p>Incorrect subtraction would lead to an erroneous voltage or resistance value, and hence an incorrect calculation of current $I$.</p> Signup and view all the answers

<p>Rounding the current can simplify the value but might lead to a loss of precision, especially in sensitive electrical applications.</p> Signup and view all the answers

<p>The arrangement, such as series or parallel, affects total resistance and therefore impacts the current and voltage calculations using Ohm's Law.</p> Signup and view all the answers

<p>Without the resistance $R$, the current $I$ cannot be determined since it relies on both voltage and resistance values.</p> Signup and view all the answers

<p>Neglecting units can lead to confusion and incorrect interpretations of values, making it impossible to validate results.</p> Signup and view all the answers

A temperature-sensitive resistor whose resistance changes with temperature.

An electromechanical switch that opens and closes circuits electronically or electromechanically.

A resistor whose resistance can be adjusted to control current flow.

A circuit that uses relays or switches to control the operation of devices such as heaters or motors.

Heater turns on when temperature falls below a set threshold due to circuit response.

Increasing resistance R causes the heater to switch on at a lower temperature.

The specific temperature level at which the heater is activated.

A principle stating that voltage equals current times resistance (V = I × R).

The electrical potential difference between two points; measured in volts.

The flow of electric charge; measured in amperes (A).

The opposition to the flow of current; measured in ohms (Ω).

Replacing variables with known values in mathematical expressions.

Adjusting numbers during calculations for simplicity, before the final answer.

The completed answer which includes numerical value and unit.

A mistake made during numerical calculations.

Digits in a number that contribute to its precision.

A period between events where actions repeat.

The time required for a quantity to reduce to half its initial value.

The number of counts detected in a given time frame, usually per minute.

The way sound travels through different mediums, allowing it to be heard.

Standard quantities (like minutes, counts per minute) used to express values.

The equivalent resistance in a circuit when multiple resistances are combined.

The Thevenin equivalent voltage in a circuit.

The specific voltage at which a device turns on or off.

A type of transistor used for switching or amplifying electronic signals.

The voltage measured across a thermistor that changes with temperature variations.

A simple circuit using resistors to reduce voltage to a desired level.

The distance a wave travels per unit of time.

The distance between two consecutive peaks of a wave.

The number of waves that pass a point in a given time.

Calculated using the formula: Speed = Frequency × Wavelength.

The bending of light rays when they pass from air into water.

An imaginary line perpendicular to the surface where light hits.

A visual representation showing the path of light rays.

Water that has little to no movement, allowing for clearer vision.

Light hitting a surface at an angle, affecting how it is perceived.

Looking into water can distort the view due to refraction.