No, the luminous clock is not radioactive. The luminescence in the clock is typically achieved using a phosphorescent material that absorbs light and then slowly releases it over time. This process does not involve any radioactive materials. The glow from the clock is simply a result of this light-absorption and emission process. **

Self-luminous bodies are objects that emit their own light, as opposed to reflecting light from another source. Examples of self-luminous bodies include stars, the sun, and certain types of light bulbs. These objects generate their own energy through processes like nuclear fusion or electrical current, which produces light as a byproduct. **

A luminous point is a theoretical concept used in physics and optics to represent a source of light that emits light in all directions. It is often used as a simplification in the study of light and its behavior, allowing for easier calculations and analysis. In reality, a luminous point does not exist as a physical object, but it is a useful tool for understanding the behavior of light in various systems. **

The luminous intensity is specified for reflector lamps because it measures the amount of light emitted in a specific direction, which is important for directional lighting applications such as spotlights and floodlights. Reflectors are designed to control and direct light in a specific direction, so specifying luminous intensity helps to ensure that the lamp is suitable for its intended purpose. Luminous flux, on the other hand, measures the total amount of visible light emitted by a source in all directions, which may not be as relevant for reflector lamps where the focus is on directing light in a specific direction. **

In physics, a self-luminous object is one that produces its own light, such as the sun or a light bulb. These objects emit light due to internal processes, such as nuclear fusion or electrical excitation. On the other hand, an externally luminous object is one that reflects light from another source, such as the moon or a mirror. These objects do not produce their own light but appear illuminated due to the light they reflect from another source. **

A digital thermometer for the bathtub works by using a temperature sensor to measure the water temperature. The sensor is usually located at the end of a probe that is placed in the water. The sensor then sends the temperature data to a digital display unit, which shows the current temperature of the water. Some digital thermometers also have additional features such as alarms for when the water reaches a certain temperature, or memory functions to track temperature changes over time. **

A digital clock is a type of clock that displays the time using numerical digits, typically in a 12-hour or 24-hour format. It uses electronic components such as LED, LCD, or VFD displays to show the time digitally, as opposed to traditional analog clocks that use mechanical hands to indicate the time. Digital clocks are often found in electronic devices such as smartphones, computers, and alarm clocks, and are known for their accuracy and ease of reading. **

The correct grammar for "outdoor thermometer in the car" is to use the adjective "outdoor" to modify the noun "thermometer," and the prepositional phrase "in the car" to indicate the location of the thermometer. This construction follows the pattern of adjective + noun + prepositional phrase. **