A thunderstorm is approaching. You are in an open field with a lone tree (10 m tall) 50 m away and a metal fence post (1.5 m tall) 40 m away. You shelter next to the tree, reasoning that lightning will strike the tallest object. Is this sound reasoning?
AYes — lightning preferentially strikes the tallest object in the area to minimize the path length to ground
BNo — lightning follows the path of least electrical resistance, not necessarily the tallest object; sheltering near any tall conductor is dangerous
CYes — trees are natural lightning rods and channel the current safely into the ground
DNo — only metal objects attract lightning; wooden trees are essentially invisible to stepped leaders
Lightning follows the path of electrical least resistance between cloud and ground. While taller objects can initiate upward return strokes more readily, 'tallest = safest target' is a dangerous oversimplification. Both the tree and the metal post could attract a strike. Standing under or near a tree during a thunderstorm is itself a leading cause of lightning fatalities; the correct action is to find a substantial building or metal-topped vehicle.
Question 2 Multiple Choice
What physical process generates the charge separation that drives lightning in a cumulonimbus cloud?
AFriction between raindrops and rising air molecules in the updraft creates static charge
BCollisions between small ice crystals rising in the updraft and larger graupel falling through the mixed-phase region transfer charge, leaving graupel negative and ice crystals positive
CIonization of air molecules by cosmic rays at cloud-top altitudes creates a charge imbalance
DPositive and negative water ions separate when liquid droplets freeze into ice crystals
In the mixed-phase region (roughly −10°C to −25°C), collisions between light ice crystals (carried upward by the updraft) and heavier graupel (falling downward) transfer negative charge to the graupel and leave positive charge on the ice crystals. The updraft carries positively charged crystals to the anvil while negatively charged graupel accumulates in the mid-levels, building the enormous voltage difference that eventually drives lightning.
Question 3 True / False
Thunder is caused by the sound of clouds colliding as they are pushed together by strong storm winds.
TTrue
FFalse
Answer: False
Thunder is the acoustic shock wave produced by the explosive expansion of air along the lightning channel. The lightning channel is heated to roughly 30,000 K in microseconds — more than five times the surface temperature of the sun. This superheated air expands violently, creating a compression wave that propagates outward as thunder. The rumble we hear (versus a sharp crack) comes from different parts of the long lightning channel arriving at our ears at slightly different times.
Question 4 True / False
A flash of lightning is observed, and thunder is heard 9 seconds later. The lightning struck approximately 3 km away.
TTrue
FFalse
Answer: True
Sound travels at approximately 340 m/s, or roughly 1 km every 3 seconds. Nine seconds × (1 km / 3 s) = 3 km. Light travels nearly instantaneously, so the time difference between flash and thunder directly encodes the distance. (The 5-second-per-mile approximation used in the US gives the same result: 9 s ÷ 5 ≈ 1.8 miles ≈ 3 km.)
Question 5 Short Answer
Why does a single-cell thunderstorm's mature stage simultaneously produce the storm's most intense weather and begin the process that leads to its own dissipation?
Think about your answer, then reveal below.
Model answer: The mature stage begins when precipitation becomes heavy enough to create a downdraft alongside the updraft. The downdraft produces the storm's worst weather — heavy rain, hail, and strong surface winds. But the same downdraft spreads across the surface, forming a gust front that undercuts and cuts off the warm, moist inflow that feeds the updraft. Without that fuel supply, the updraft weakens and the storm dies. The downdraft is both the source of the storm's intensity and the mechanism of its destruction.
This self-limiting nature of single-cell storms is a key insight. Supercell and multi-cell storms evade this by having the updraft and downdraft spatially separated, allowing the inflow to continue uninterrupted — which is why they persist for hours rather than the 30–60 minutes typical of single cells.