"caustic surface" meaning in English

{
  "forms": [
    {
      "form": "caustic surfaces",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "caustic surface (plural caustic surfaces)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "langcode": "en",
          "name": "Optics",
          "orig": "en:Optics",
          "parents": [],
          "source": "w"
        }
      ],
      "examples": [
        {
          "text": "Caustic curves and surfaces are called catacaustic when formed by reflection, and diacaustic when formed by refraction."
        }
      ],
      "glosses": [
        "A surface to which rays reflected or refracted by another surface are tangents."
      ],
      "id": "en-caustic_surface-en-noun-njFkz7xx",
      "links": [
        [
          "optics",
          "optics"
        ]
      ],
      "raw_glosses": [
        "(optics) A surface to which rays reflected or refracted by another surface are tangents."
      ],
      "related": [
        {
          "word": "caustic"
        },
        {
          "word": "caustic curve"
        },
        {
          "word": "focus"
        }
      ],
      "topics": [
        "engineering",
        "natural-sciences",
        "optics",
        "physical-sciences",
        "physics"
      ]
    }
  ],
  "word": "caustic surface"
}

{
  "forms": [
    {
      "form": "caustic surfaces",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "caustic surface (plural caustic surfaces)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "related": [
    {
      "word": "caustic"
    },
    {
      "word": "caustic curve"
    },
    {
      "word": "focus"
    }
  ],
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "Pages with 1 entry",
        "Pages with entries",
        "en:Optics"
      ],
      "examples": [
        {
          "text": "Caustic curves and surfaces are called catacaustic when formed by reflection, and diacaustic when formed by refraction."
        }
      ],
      "glosses": [
        "A surface to which rays reflected or refracted by another surface are tangents."
      ],
      "links": [
        [
          "optics",
          "optics"
        ]
      ],
      "raw_glosses": [
        "(optics) A surface to which rays reflected or refracted by another surface are tangents."
      ],
      "topics": [
        "engineering",
        "natural-sciences",
        "optics",
        "physical-sciences",
        "physics"
      ]
    }
  ],
  "word": "caustic surface"
}