Who won the Nobel Prize in Physics in 2015 for the discovery of neutrino oscillations showing that neutrinos have mass?

Introduction / Context:
This question tests your knowledge of recent Nobel Prize winners in physics. It specifically asks about the 2015 Nobel Prize in Physics, which was awarded for the discovery of neutrino oscillations, a result that proved neutrinos have mass. You must identify which scientist from the options received this honour.

Given Data / Assumptions:

• The year is 2015.
• The field is Physics.
• The prize recognised the discovery of neutrino oscillations and the fact that neutrinos have mass.
• The options are Hiroshi Amano, Takaaki Kajita, Isamu Akasaki, Makoto Kobayashi, and Shuji Nakamura.

Concept / Approach:
The Nobel Prize in Physics in 2015 was shared by two scientists, Takaaki Kajita from Japan and Arthur B McDonald from Canada, for their work on neutrino oscillations. Among the listed options, only Takaaki Kajita matches this description and year. The other names are Nobel laureates in physics, but for different discoveries and in different years.

Step-by-Step Solution:
Step 1: Recall the official citation for the 2015 Nobel Prize in Physics: it was awarded for the discovery of neutrino oscillations, which shows that neutrinos have mass.Step 2: Remember that this prize was shared between Takaaki Kajita and Arthur B McDonald.Step 3: Examine the options. Takaaki Kajita is present, but Arthur B McDonald is not listed.Step 4: Recognise that Hiroshi Amano, Isamu Akasaki, and Shuji Nakamura received the Nobel Prize in Physics in 2014 for the invention of efficient blue light emitting diodes, while Makoto Kobayashi was honoured in 2008 for work on symmetry breaking in particle physics.Step 5: Therefore, the only option consistent with the 2015 Nobel Prize in Physics for neutrino oscillations is Takaaki Kajita.

Verification / Alternative check:
The official Nobel Prize website lists Takaaki Kajita and Arthur B McDonald as the 2015 physics laureates for their key contributions to experiments demonstrating neutrino oscillations. Popular science articles and physics news reports from 2015 also highlight their work and mention Kajita by name. Comparing this with information about the other listed scientists confirms that they were associated with other Nobel years or different discoveries.

Why Other Options Are Wrong:

• Hiroshi Amano: Co recipient of the 2014 Nobel Prize in Physics for the invention of efficient blue LEDs, not for neutrino oscillations in 2015.
• Isamu Akasaki: Another 2014 physics laureate for blue LEDs, so he does not match the 2015 prize for neutrinos.
• Makoto Kobayashi: Awarded the 2008 Nobel Prize in Physics for work on the origin of broken symmetry that predicts the existence of at least three families of quarks, not for neutrino oscillations.
• Shuji Nakamura: Along with Akasaki and Amano, received the 2014 Nobel Prize in Physics for blue LEDs, not the 2015 prize.

Common Pitfalls:
Students often confuse nearby years or mix up different Nobel winning discoveries in physics, especially when several Japanese physicists appear among the laureates. Another common error is to recognise a familiar name like Shuji Nakamura or Isamu Akasaki and select it without checking whether the discovery and year match the question. Always tie the name, year, and discovery together when answering Nobel Prize questions.

Final Answer:
Takaaki Kajita won the Nobel Prize in Physics in 2015 for the discovery of neutrino oscillations showing that neutrinos have mass, so option B is correct.