Understanding the Longest Day in the Northern Hemisphere

The question asks about the timing of the longest day of the year in the Northern Hemisphere. The longest day refers to the day with the maximum number of daylight hours. This astronomical event is known as the Summer Solstice.

What is the Summer Solstice?

The Summer Solstice occurs when one of Earth's poles is tilted closest to the Sun. This results in the Sun reaching its highest position in the sky relative to the celestial equator on that day, leading to the longest period of daylight and shortest night of the year in the hemisphere tilted towards the Sun.

Why the Longest Day Occurs in June in the Northern Hemisphere

The Earth orbits the Sun on a tilted axis, approximately $23.5^\circ$. This tilt is responsible for the seasons. When the Northern Hemisphere is tilted towards the Sun, it experiences summer. The peak tilt towards the Sun occurs around June 20th or 21st each year. This specific date marks the Summer Solstice in the Northern Hemisphere.

Because the Northern Hemisphere is most directly illuminated by the Sun around this time, the path of the Sun across the sky is highest and longest, resulting in the maximum duration of daylight for locations in the Northern Hemisphere.

Analyzing the Options

Let's look at the given options in the context of the Summer Solstice occurring around June 20th or 21st:

• Option 1: First half of the month of June (June 1st to June 15th). This period is before the typical Summer Solstice date.
• Option 2: Second half of the month of June (June 16th to June 30th). This period includes the typical Summer Solstice dates of June 20th or 21st.
• Option 3: First half of the month of July (July 1st to July 15th). This period is after the Summer Solstice. Days start getting shorter in the Northern Hemisphere after the solstice.
• Option 4: Second half of the month of July (July 16th to July 31st). This period is well after the Summer Solstice, and days are noticeably shorter than in late June.

Since the Summer Solstice, the day with the most daylight, typically falls on June 20th or 21st, it occurs in the second half of the month of June.

Conclusion

Based on the astronomical event of the Summer Solstice, which brings the longest day to the Northern Hemisphere, this event normally takes place in the second half of June.

Revision Table: Solstices and Equinoxes

Additional Information: Earth's Tilt and Daylight Hours

The Earth's axial tilt ($23.5^\circ$) is the primary reason for the variation in daylight hours throughout the year and across different latitudes. During the Northern Hemisphere's summer, the tilt towards the Sun means:

• Higher sun angle at noon.
• Longer path of the sun across the sky.
• More direct sunlight.
• Longer days and shorter nights.

The effect is more pronounced at higher latitudes. Locations north of the Arctic Circle ($66.5^\circ$ N) experience 24 hours of daylight (Midnight Sun) around the Summer Solstice.

Conversely, during the Winter Solstice in December, the Northern Hemisphere is tilted away from the Sun, resulting in the shortest day and longest night of the year.