Who is credited with the key practical development of radar technology that made it usable for detecting aircraft?

Introduction / Context:
This question asks about the history of radar, a technology used to detect objects such as aircraft and ships by using radio waves. Radar played a crucial role during the Second World War, especially in air defence. Many scientists contributed to radio and electromagnetic theory, but one name is particularly linked with the development of practical radar systems in the United Kingdom: Robert Watson Watt. Recognising his name is important in the inventions section of general knowledge.

Given Data / Assumptions:

• The technology in question is radar, which uses radio waves to detect and locate objects.
• The options given are Henrey Backquerel, Max Planck, Robert Watson Watt and Humphrey Davy.
• The question seeks the scientist most directly associated with the practical development of radar.
• Standard exam references are taken as the basis for the expected answer.

Concept / Approach:
Henri Becquerel discovered radioactivity, which is a different phenomenon. Max Planck is known as the father of quantum theory. Humphry Davy is remembered for work in chemistry, including the Davy lamp and electrochemistry. Robert Watson Watt, on the other hand, worked on radio direction finding and is widely credited with leading the development of early radar systems in Britain. This innovation allowed military forces to detect incoming aircraft and contributed significantly to air defence strategies.

Step-by-Step Solution:
Step 1: Identify radar as a radio based detection system, used to locate aircraft and ships by sending out radio pulses and receiving echoes. Step 2: Recall that Robert Watson Watt is often called the father of radar because of his leadership in transforming theoretical ideas into practical air defence systems before and during the Second World War. Step 3: Recognise that Henri Becquerel is connected with the discovery of radioactivity, not radar. Step 4: Remember that Max Planck introduced quantum theory, a different area of physics. Step 5: Note that Humphry Davy made important chemical discoveries and invented a safety lamp for miners, not a radar system. Step 6: Conclude that Robert Watson Watt is the only option that matches the development of radar technology, and select him as the correct answer.

Verification / Alternative check:
A quick verification can be made by recalling that in many exam oriented lists of inventions, radar is matched with Robert Watson Watt. Additionally, one may remember that radar stands for radio detection and ranging, linking it to radio engineering rather than nuclear physics or chemistry. This helps rule out Becquerel and Davy. Planck's main field was theoretical quantum physics, again not directly connected to applied radio detection systems, confirming the answer.

Why Other Options Are Wrong:
Henri Becquerel studied emissions from uranium salts and discovered radioactivity, which relates to nuclear phenomena, not radar. Max Planck proposed the quantum of action, starting quantum mechanics, but did not design radar equipment. Humphry Davy performed experiments in electrochemistry and invented the miners safety lamp. None of these contributions involve the development of radar systems, making these options incorrect for this specific question.

Common Pitfalls:
Learners sometimes confuse any discovery that involves the word radio or radiation and pick scientists connected with radioactivity or electromagnetic theory in general. Another common error is guessing based on unfamiliar names without recalling which field each scientist worked in. To avoid this, it is useful to tie each major technological invention to one or two key individuals, such as Watson Watt for radar, Marconi for wireless telegraphy and Becquerel for radioactivity.

Final Answer:
The scientist most closely associated with the practical development of radar technology is Robert Watson Watt.