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Difficulty: MediumNegative Detail Identification

Modern military night-vision goggles rely on image intensifier tubes to amplify ambient light in dark environments. Incoming photons enter through an objective lens and strike a photocathode, which converts light energy into a stream of free electrons. These electrons are accelerated by an electrical field into a microchannel plate (MCP), a thin glass disc containing millions of microscopic channels that multiply the electrons through secondary emission. The amplified electron cascade then impacts a phosphor screen, converting kinetic electrical energy back into visible green photons viewed through the ocular eyepiece. While the intensifier tube magnifies ambient moonlight and starlight thousands of times, it requires an external high-voltage power supply and cannot function in absolute darkness without active infrared illumination.

According to the passage, which of the following statements about image intensifier tubes is NOT accurate?

  1. A
    The photocathode converts incoming light photons into a stream of free electrons.
  2. They can amplify ambient light in total darkness without auxiliary infrared illumination.Answer
  3. C
    A microchannel plate multiplies the electron cascade using secondary emission.
  4. D
    An external high-voltage power supply is necessary for the system to operate.

Answer

Image intensifier tubes cannot amplify ambient light in total darkness without auxiliary infrared illumination.
The statement asserting that image intensifier tubes can amplify ambient light in total darkness without auxiliary infrared illumination is contradicted by the passage. The final sentence explicitly notes that while the tube magnifies ambient moonlight and starlight, it 'cannot function in absolute darkness without active infrared illumination.' Therefore, this statement is inaccurate based on the text.

Step-by-Step Solution

1
Identify the negative qualifier in the stem
Recognize that the prompt asks for the statement that is NOT accurate according to the provided text.
Negative detail questions require identifying the false, contradicted, or unmentioned assertion among true supporting details.
2
Scan the passage to verify each candidate choice against explicit textual facts
The text explicitly confirms that the photocathode converts photons to electrons, the microchannel plate uses secondary emission, and an external high-voltage supply is required.
Eliminating true, verified facts isolates the single contradicted or unstated claim.
3
Evaluate the remaining statement regarding performance in total darkness
The text states that the device 'cannot function in absolute darkness without active infrared illumination', directly contradicting the claim that it operates in total darkness without auxiliary illumination.
Direct textual contradiction establishes this statement as the correct answer to the negative inquiry.

Key Concept

Negative Detail Identification in Technical Passages
Estimated Time:1m 0s
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Topics

Negative Detail Identification

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