Solutions The combination of waves of the same wavelength from two or more sources producing a new wave pattern has 6 entries with similar clues

• 7-letter words
• comptonAmerican physicist who showed that the wavelength of X-rays increased when scattered by electrons
• dopplerAustrian physicist, d. 1853, famous for his discovery of the effect of movement on perceived wavelengths
• shudderShake from/with fear
• 8-letter words
• deadlockSituation from/in which no progress can be made
• infraredOf radiation with a longer wavelength than light
• 9-letter words
• strollersthey slowly progress a little way over the waves